Motor

ABSTRACT

A rotor of a motor includes first and second rotor cores, a field magnet, and a commutator magnet. The first and second rotor cores each include a core base and a plurality of claw poles. The claw poles of the first rotor core and the claw poles of the second rotor core are alternately arranged in a circumferential direction. The field magnet is located between the core bases. The field magnet is magnetized in an axial direction so that the claw poles of the first rotor core and the claw poles of the second rotor core function as different magnetic poles in the circumferential direction. The commutator magnet is located on an outer circumference of the field magnet around the claw poles. The commutator magnet is magnetized so that surfaces having the same polarity face each other between the claw poles and the commutator magnet.

RELATED APPLICATION

This application is a division of application Ser. No. 14/975,394 filedDec. 18, 2015, which claims the benefit of Japanese Application No.2015001484 filed Jan. 7, 2015, Japanese Application No. 2015023061 filedFeb. 9, 2015, Japanese Application No. 2015030688 filed Feb. 19, 2015,Japanese Application No. 2015033158 filed Feb. 23, 2015, JapaneseApplication No. 2015078554 filed Apr. 7, 2015, Japanese Application No.2015144312 filed Jul. 21, 2015, each of which is hereby fullyincorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a motor.

Japanese Laid-Open Patent Application No. 2012-115085 describes anexample of a rotor having a permanent magnet field Lundellconfiguration. In the prior art, the rotor is used in a motor. The rotorincludes two rotor cores, which are stacked upon each other, and a fieldmagnet, which is disk-shape and located between the rotor cores. Each ofthe rotor cores includes a plurality of claw poles arranged in acircumferential direction. The field magnet causes the claw poles of therotor cores to function as poles that alternately change in thecircumferential direction.

In addition to the field magnet, the rotor described in JapaneseLaid-Open Patent Publication No. 2012-115085 includes back surfacemagnets and interpolar magnets that serve as commutator magnets. Each ofthe back surface magnets is located on a back surface of a claw pole,that is, between the claw pole and the field magnet. Each of theinterpolar magnets is located between claw poles that are adjacent toeach other in the circumferential direction. The commutator magnetsreduce leakage flux of the rotor.

In a rotor that includes commutator magnets, there is no description ofhow the commutator magnets are fixed in the rotor, and there is a needfor fixing the commutator magnets in a desirable manner.

Furthermore, an interior permanent magnet (IPM) rotor that has magnetsembedded in a rotor core is known in the art (refer to, for example,Japanese Laid-Open Patent Publication No. 2002-252947). The rotordisclosed in Japanese Laid-Open Patent Publication No. 2002-252947includes a rotor core including a plurality of insertion holes arrangedin the circumferential direction. Magnets are inserted in the insertionholes so that magnets with magnetic poles functioning as the N poles onthe outer side in the radial direction and magnets with magnetic polesfunctioning as S poles on the outer side in the radial direction arealternately arranged in the circumferential direction.

The rotor disclosed in Japanese Laid-Open Patent Publication No.2002-252947 includes a plurality of magnets. This increases the numberof components. Thus, there is room for improvement in terms ofassembling efficiency.

In the motor disclosed in Japanese Laid-Open Patent Publication No.2012-115085, magnetic saturation may occur in the claw poles of therotor core. In the magnetic flux generated by the field magnet, themagnetic saturation lowers the ratio of the magnetic flux that iseffective for the rotation of the rotor. Thus, the desired output cannotbe obtained.

SUMMARY OF THE INVENTION

A first object of the present invention is to provide a motor in whichcommutator magnets are fixed in a desirable manner. A second object ofthe present invention is to provide a motor that improves the assemblingefficiency and limits increases in the number of components. A thirdobject of the present invention is to provide a motor that improves theoutput.

To achieve the above object, a motor according to a first aspect of thepresent invention includes a rotor. The rotor includes first and secondrotor cores, a field magnet, and a commutator magnet. The first andsecond rotor cores each include a disk-shaped core base and a pluralityof claw poles arranged in a circumferential direction on an outercircumferential portion of the core base. The first and second rotorcores are stacked upon each other in an axial direction so that the clawpoles of the first rotor core and the claw poles of the second rotorcore are alternately arranged in the circumferential direction. Thefield magnet is located between the core base of the first rotor coreand the core base of the second rotor core. The field magnet ismagnetized in the axial direction so that the claw poles of the firstrotor core and the claw poles of the second rotor core function asdifferent magnetic poles in the circumferential direction. Thecommutator magnet is located on an outer circumference of the fieldmagnet and near the claw poles. The commutator magnet is magnetized sothat surfaces having the same polarity face each other in the claw polesand the commutator magnet.

To achieve the above object, a motor according to a second aspect of thepresent invention includes a rotor. The rotor includes a rotor core anda field magnet. The rotor core includes a substantially disk-shaped corebase and a plurality of claw poles that extend at least in an axialdirection from an outer circumferential portion of the core base. Theclaw poles are arranged in a circumferential direction. The field magnetcontacts the claw poles in a radial direction and is anisotropicallyoriented so that the plurality of claw poles function as differentmagnetic poles in the circumferential direction.

To achieve the above object, a motor according to a third aspect of thepresent invention includes a rotor and a stator. The rotor including afirst rotor core, a second rotor core, and a field magnet magnetized inan axial direction. The first rotor core and the second rotor core eachinclude a plurality of claw poles arranged in a circumferentialdirection. The first rotor core and the second rotor core are joinedwith each other so that the claw poles of the first rotor core and theclaw poles of the second rotor core are alternately arranged in thecircumferential direction. The field magnet is located between the firstrotor core and the second rotor core so that the claw poles of the firstrotor core and the claw poles of the second rotor core function asalternately differing magnetic poles. The stator includes a stator coreand a coil wound around the stator core. The coil generates a rotatingmagnetic field that acts on the rotor. The claw poles each include aradially opposing portion, which opposes the stator core in the radialdirection, and an axially opposing portion, which opposes the statorcore in the axial direction.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a motor according to a firstembodiment of the present invention.

FIG. 2 is an exploded perspective view of a rotor illustrated in FIG. 1.

FIG. 3 is a perspective view of a rotor core illustrated in FIG. 2.

FIG. 4 is a perspective view of a commutator magnet illustrated in FIG.2.

FIG. 5 is a partially enlarged view of the rotor illustrated in FIG. 1.

FIG. 6 is a perspective view of the rotor illustrated in FIG. 1.

FIG. 7 is a cross-sectional view of the rotor illustrated in FIG. 6.

FIG. 8 is an exploded perspective view of a rotor according to a secondembodiment of the present invention.

FIGS. 9A and 9B are cross-sectional views of the rotor illustrated inFIG. 8.

FIG. 10 is a partially enlarged view of a rotor in a modification of thefirst embodiment.

FIG. 11 is a partially enlarged view of a rotor in a modification of thefirst embodiment.

FIG. 12 is a partially enlarged view of a rotor in a modification of thefirst embodiment.

FIG. 13 is a partially enlarged view of a rotor in a modification of thefirst embodiment.

FIG. 14 is a partial cross-sectional view of a motor according to athird embodiment of the present invention.

FIG. 15 is a partial cross-sectional view of the motor illustrated inFIG. 14.

FIG. 16 is a perspective view of a rotor illustrated in FIG. 15.

FIG. 17 is a partially enlarged cross-sectional view of the rotorillustrated in FIG. 16.

FIGS. 18A and 18B are schematic cross-sectional views showing a methodfor manufacturing the rotor illustrated in FIG. 16.

FIG. 19 is a perspective view of an anisotropic magnet in a modificationof the third embodiment.

FIGS. 20A and 20B are schematic cross-sectional views showing a methodfor manufacturing a rotor in a modification of the third embodiment.

FIGS. 21A and 21B are schematic cross-sectional views showing a methodfor manufacturing a rotor in a modification of the third embodiment.

FIGS. 22A and 22B are schematic cross-sectional views showing a methodfor manufacturing a rotor in a modification of the third embodiment.

FIGS. 23A and 23B are schematic cross-sectional views showing a methodfor manufacturing a rotor in a modification of the third embodiment.

FIG. 24 is a partial perspective view for describing a protrusion in amodification of the third embodiment.

FIG. 25 is a partial perspective view showing a protrusion in amodification of the third embodiment.

FIG. 26 is an exploded perspective view showing a rotor in amodification of the third embodiment.

FIGS. 27A and 27B are schematic side views showing a method formanufacturing a rotor in a modification of the third embodiment.

FIGS. 28A and 28B are schematic side views showing a method formanufacturing a rotor in a modification of the third embodiment.

FIGS. 29A and 29B are schematic plan views showing a method formanufacturing a rotor in a modification of the third embodiment.

FIG. 30 is a partial cross-sectional view of a brushless motor accordingto a fourth embodiment of the present invention.

FIG. 31 is a partial cross-sectional view of a rotor illustrated in FIG.30.

FIG. 32 is a perspective view of the rotor illustrated in FIG. 31.

FIG. 33 is an exploded perspective view of the rotor illustrated in FIG.32

FIG. 34 is a cross-sectional view taken along line A-A in FIG. 31.

FIG. 35 is a perspective view of an integrated permanent magnet in amodification of the fourth embodiment.

FIG. 36A is a perspective view of an integrated permanent magnet in amodification of the fourth embodiment.

FIG. 36B is a cross-sectional view of the integrated permanent magnetillustrated in FIG. 36A.

FIG. 37 is a partial cross-sectional view of a rotor according to afifth embodiment of the present invention.

FIG. 38 is a partial cross-sectional view of a rotor in a modificationof the fifth embodiment.

FIG. 39 is a cross-sectional view of a motor according to a sixthembodiment of the present invention.

FIG. 40 is an exploded perspective view of a rotor illustrated in FIG.39.

FIG. 41 is a perspective view of the rotor illustrated in FIG. 40.

FIG. 42 is a cross-sectional view of the rotor illustrated in FIG. 41.

FIG. 43 is a perspective view of a rotor core in a modification of thesixth embodiment.

FIG. 44 is a plan view of a rotor including the rotor core illustratedin FIG. 43.

FIG. 45 is an exploded perspective view of a rotor in a modification ofthe sixth embodiment.

FIG. 46 is a perspective view of the rotor illustrated in FIG. 45.

FIG. 47 is a plan view of the rotor illustrated in FIG. 46.

FIG. 48 is a partial cross-sectional perspective view of a motoraccording to a seventh embodiment of the present invention.

FIG. 49 is an exploded perspective view of a rotor illustrated in FIG.48.

FIG. 50 is a cross-sectional view of the motor illustrated in FIG. 48.

FIG. 51 is a cross-sectional view of a motor in a modification of theseventh embodiment.

FIG. 52 is a perspective view of a first rotor core illustrated in FIG.51.

FIG. 53 is an exploded perspective view of the first rotor coreillustrated in FIG. 52.

FIG. 54 is a cross-sectional view of a motor in a modification of theseventh embodiment.

FIG. 55 is a perspective view of a first rotor core illustrated in FIG.54.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

A motor according to a first embodiment will now be described.

A motor 1 of the present embodiment illustrated in FIG. 1 is a brushlessmotor. A motor casing 2, serving as a shell of the motor 1, includes ayoke housing 3, which is cylindrical and has a closed end, and an endplate 4, which closes an opening of the yoke housing 3.

A stator 5, having an annular shape, is fixed to an innercircumferential surface of the yoke housing 3. The stator 5 includes astator core 6 a plurality of teeth 6 a, which extends inward in a radialdirection, and coils 8, which are wound around the teeth 6 a with aninsulator 7 arranged in between. The stator 5 generates a rotatingmagnetic field when an external control circuit S supplies drivingcurrent to the coil 8.

A rotor 11 is located at an inner side of the stator 5. Two bearings 12and 13 are respectively arranged on a central portion of the closed endof the yoke housing 3 and a central portion of the end plate 4. The twobearings 12 and 13 rotationally support a rotation shaft 14 of the rotor11. The end of the rotation shaft 14 closer to the end plate 4 in theaxial direction extends through the end plate and protrudes outward fromthe motor casing 2.

The rotor 11 includes two rotor cores (i.e., first rotor core 15 andsecond rotor core 16) fixed to the rotation shaft 14, a field magnet 17located between the first rotor core 15 and the second rotor core 16,and a single commutator magnet 18 arranged on the outer circumference ofthe field magnet 17.

As illustrated in FIGS. 2 and 3, the first rotor core 15 includes adisk-shaped first core base 21 and a plurality of (five in the presentembodiment) first claw poles 22 arranged in a circumferential directionon an outer circumferential portion of the first core base 21. A throughhole 21 a, in which the rotation shaft 14 is inserted and fixed, extendsthrough a radially central portion of the first core base 21. The fivefirst claw poles 22 are arranged at equal intervals (interval of 72°) onthe outer circumferential portion of the first core base 21 in thecircumferential direction.

The first claw poles 22 each include a first radially extending portion22 a, which extends outward from the outer circumferential portion ofthe first core base 21 in the radial direction, and a first axiallyextending portion 22 b, which projects toward one side in the axialdirection from a distal end (radially outer end) of the first radiallyextending portion 22 a.

The first radially extending portion 22 a has a sectoral shape as viewedin the axial direction that widens in the circumferential directiontoward the outer side in the radial direction. The first axiallyextending portion 22 b has a sectoral cross-sectional shape in adirection orthogonal to the axial direction that widens in thecircumferential direction toward the outer side in the radial direction.The first claw poles 22 each have two circumferential side surfaces thatare flat and parallel to an axis of the rotation shaft 14. The radiallyouter side surfaces of the first axially extending portions 22 b arearcuate and lie along the same circle extending about the rotation axisof the rotor 11, as viewed in the axial direction. Each first claw pole22 is symmetrical in shape with respect to a plane of symmetry thatextends through a circumferential centroid of the first claw pole 22 andis orthogonal to the circumferential direction.

Referring to FIGS. 3 and 5, the radially inner surface of the firstaxially extending portion 22 b of each first claw pole 22 defines afirst core fixed surface 22 c that is fixed to the commutator magnet 18by an adhesive 41. The first core fixed surface 22 c are arcuate and liealong the same circle extending about the rotation axis of the rotor 11,as viewed in the axial direction. The first core fixed surfaces 22 ceach include a first collection recess 22 d. The first collectionrecesses 22 d are each formed in the circumferentially central portionof the corresponding one of the first core fixed surfaces 22 c and eachhave a shape of a groove extending in the axial direction. The firstcollection recess 22 d extends over the first core fixed surface 22 cfrom one end to the other end of in the axial direction. The firstcollection recesses 22 d each have a cross-section in a directionorthogonal to the axial direction that is uniformly shaped from one endto the other end of the first collection recess 22 d in the axialdirection and rectangular in shape so as to have a constant width in thecircumferential direction. Each first collection recess 22 d opens atthe radially inner side in the radial direction and at the two axialsides.

As illustrated in FIG. 2, the second rotor core 16, which is identicalin shape to the first rotor core 15, includes a second core base 23 anda plurality of (five in the present embodiment) second claw poles 24that are arranged in the circumferential direction on an outercircumferential portion of the second core base 23. The second core base23 includes a through hole 23 a, in which the rotation shaft 14 isinserted and fixed, and is identical in shape to the first core base 21,which includes the through hole 21 a. Each of the second claw poles 24includes a second radially extending portion 24 a and a second axiallyextending portion 24 b. Further, the second claw poles 24 are identicalin shape to the first claw poles 22, each including the first radiallyextending portion 22 a and the first axially extending portion 22 b.

The second claw poles 24 each have a second core fixed surface 24 c,which is fixed to the commutator magnet 18 by the adhesive 41 (not shownin FIG. 2) and serves as a radially inner side surface of the secondaxially extending portion 24 b. The second core fixed surface 24 c isidentical in shape to the first core fixed surface 22 c (see FIG. 3).The second core fixed surface 24 c includes a second collection recess24 d, which is identical in shape to the first collection recess 22 d(see FIG. 3).

As illustrated in FIGS. 1, 2, and 6, the rotation shaft 14 ispress-fitted into the through holes 21 a and 23 a to fix the first rotorcore 15 and the second rotor core 16 while maintaining an axial intervalin between. The first and second rotor cores 15 and 16 are fixed to therotation shaft 14 with the field magnet 17 and the commutator magnet 18held between the first rotor core 15 and the second rotor core 16. Thefirst rotor core 15 and the second rotor core 16 are fixed to therotation shaft 14 stacked upon each other in the axial direction. Distalends of the first axially extending portions 22 b face directionsopposite to distal ends of the second axially extending portions 24 b.Further, the second claw poles 24 are located between the first clawpoles 22 that are adjacent in the circumferential direction. The firstaxially extending portions 22 b and the second axially extendingportions 24 b of the first and second rotor cores 15 and 16, which arefixed to the rotation shaft 14, are alternately arranged in thecircumferential direction at equal intervals (interval of 36°) in thecircumferential direction.

As illustrated in FIGS. 1, 2, and 7, when the first and second rotorcores 15 and 16 are coupled to each other, the field magnet 17 islocated between the first core base 21 and the second core base 23 thatare parallel to each other. For example, the field magnet 17 is adisk-shaped permanent magnet and formed by a ferrite magnet. A throughhole 17 a, through which the rotation shaft 14 is inserted, extendsthrough the radially central portion of the field magnet 17. The fieldmagnet 17 has one axial end surface (upper end surface as viewed in FIG.2) and another axial end surface (lower end surface as viewed in FIG. 2)that are respectively in contact with the first core base 21 and thesecond core base 23. Further, the field magnet 17 is held and fixedbetween the first core base 21 and the second core base 23 in the axialdirection. The field magnet 17 has the same outer diameter as the corebases 21 and 23.

The field magnet 17 is magnetized in the axial direction so that thefirst claw pole 22 functions as the N pole and the second claw pole 24functions as the S pole. More specifically, the field magnet 17 ismagnetized in the axial direction so that the portion closer to thefirst core base 21 serves as the N pole and a portion closer to thesecond core base 23 serving as the S pole. This results in the first andsecond claw poles 22 and 24 functioning as different magnetic poles inthe circumferential direction. In this manner, the rotor 11 of thepresent embodiment is a Lundell rotor that uses the field magnet 17. Therotor 11 includes the five first claw poles 22, each serving as the Npole, and the five second claw poles 24, each serving as the S pole,that are alternately arranged in the circumferential direction. Thus,the rotor 11 includes a total of ten poles (five magnetic pole pairs).

With reference to FIGS. 2 and 4, the commutator magnet 18 is formed by aneodymium bonded magnet, for example. The commutator magnet 18 has anannular shape, surrounds the outer circumference of the field magnet 17,and is arranged on the outer circumference of the field magnet 17 nearthe first and second claw poles 22 and 24. The commutator magnet 18includes first and second back surface magnet portions 31 and 32 andfirst and second interpolar magnet portions 33 and 34.

As illustrated in FIGS. 4, 6, and 7, the first back surface magnetportion 31 is located between a back surface of each first claw pole 22of the first rotor core 15 (i.e., radially inner surface, first corefixed surface 22 c in present embodiment) and an outer circumferentialsurface 23 b of the second core base 23. The second back surface magnetportion 32 is located between a back surface of each second claw pole 24of the second rotor core 16 (i.e., radially inner surface, second corefixed surface 24 c in present embodiment) and an outer circumferentialsurface 21 b of the first core base 21. Thus, the commutator magnet 18includes five first back surface magnet portions 31, which are arrangedat equal intervals (interval of 72°) in the circumferential direction,and the second back surface magnet portions 32 that are located betweencorresponding the first back surface magnet portions 31 that areadjacent in the circumferential direction. The first back surface magnetportions 31 and the second back surface magnet portions 32 arealternately arranged at an interval of 36° in the circumferentialdirection.

As illustrated in FIGS. 4, 5, and 6, each of the first back surfacemagnet portions 31 is arcuate and has a constant width in the radialdirection. The width of the each of the first back surface magnetportions 31 in the radial direction is substantially equal to the valueof the interval between the first core fixed surface 22 c and the outercircumferential surface 23 b of the second core base 23. An outer radialsurface of each first back surface magnet portion 31 defines a firstmagnet fixed surface 31 a fixed to the first core fixed surface 22 c bythe adhesive 41. The first magnet fixed surface 31 a is arcuate and hassubstantially the same curvature as the first core fixed surface 22 c.The inner radial surface of the first back surface magnet portion 31 isarcuate and has substantially the same curvature as the outercircumferential surface 23 b of the second core base 23. Each of thefirst back surface magnet portions 31 has one circumferential end (endin counterclockwise direction as viewed in FIG. 4) formed integrallywith an first interpolar magnet portion 33 and another circumferentialend (end in clockwise direction as viewed in FIG. 4) formed integrallywith the second interpolar magnet portion 34.

Each of the second back surface magnet portions 32 is identical in shapeto the first back surface magnet portion 31. The first back surfacemagnet portion 31 is formed on one axial side (lower side as viewed inFIG. 4) of the first and second interpolar magnet portions 33 and 34,and the second back surface magnet portion 32 is formed on the otheraxial side (upper side as viewed in FIG. 4) of the first and secondinterpolar magnet portions 33 and 34. An outer radial surface of eachsecond back surface magnet portions 32 defines a second magnet fixedsurface 32 a fixed to the second core fixed surface 24 c by the adhesive41. The second magnet fixed surface 32 a is arcuate and hassubstantially the same curvature as the second core fixed surface 24 c.

The first back surface magnet portion 31 is magnetized so that theregion facing the first core fixed surface 22 c of the first claw pole22 serves as the N pole, which is the same as the first claw pole 22,and the region facing the outer circumferential surface 23 b of thesecond core base 23 serves as the S pole, which is the same as thesecond core base 23. The second back surface magnet portion 32 ismagnetized so that the region facing the second core fixed surface 24 cof the second claw pole 24 serves as the S pole, which is the same asthe second claw pole 24, and the region facing the outer circumferentialsurface 21 b of the first core base 21 serves as the N pole, which isthe same as the first core base 21.

As illustrated in FIGS. 4 to 7, the first and second interpolar magnetportions 33 and 34 are each located between the first and second clawpoles 22 and 24 that are adjacent to each other in the circumferentialdirection. More specifically, the first interpolar magnet portion 33 islocated between one circumferential end surface 22 e (counterclockwiseend surface as viewed in FIG. 6) of a first claw pole 22 and the othercircumferential end surface 24 e (clockwise end surface as viewed inFIG. 6) of a second claw pole 24. The second interpolar magnet portion34 is located between the other circumferential end surface 22 f(clockwise end surface as viewed in FIG. 6) of a first claw pole 22 andone circumferential end surface 24 f (counterclockwise end surface asviewed in FIG. 6) of a second claw pole 24.

The first interpolar magnet portion 33 is post-like and has a sectoralcross-section in a direction orthogonal to the axial direction. Thefirst interpolar magnet portion 33 has a circumferential width that issubstantially the same as the interval between one circumferential endsurface 22 e of the first claw pole 22 and the other circumferential endsurface 24 e of the second claw pole 24. The first interpolar magnetportion 33 has substantially the same radial width as the first clawpole 22. The first interpolar magnet portion 33 has the same axiallength as the first claw pole 22. The radially outer surfaces of thefirst interpolar magnet portions 33 and the radially outer surfaces ofthe first and second claw poles 22 and 24 lie along the same circleextending about the rotation axis of the rotor 11, as viewed in theaxial direction. The second interpolar magnet portion 34 is identical inshape to the first interpolar magnet portion 33. The first and secondinterpolar magnet portions 33 and 34 are magnetized in thecircumferential direction so that the surfaces of the first and secondclaw poles 22 and 24 have the same polarity as the opposing first andsecond interpolar magnet portions 33 and 34. More specifically, thefirst and second interpolar magnet portions 33 and 34 are eachmagnetized in the circumferential direction so that the region closer tothe first claw pole 22 serves as the N pole and the region closer to thesecond claw pole 24 serves as the S pole.

As illustrated in FIG. 1, a sensor magnet 52 is fixed to the rotationshaft 14 by a disk-shaped sensor magnet holder 51. The sensor magnetholder 51 is fitted and fixed to the outer portion of the rotation shaft14 between the bearing 13 and the first rotor core 15. The sensor magnetholder 51 has an outer diameter that is smaller than that of the firstrotor core 15 and larger than that of the first core base 21. The sensormagnet 52 is annular and extends along the outer circumferential portionof the sensor magnet holder 51. The sensor magnet 52 faces the firstclaw poles 22 in the axial direction with the sensor magnet holder 51located in between. The sensor magnet 52 is magnetized so that the N andthe S poles are alternately arranged in the circumferential direction.

The end plate 4 includes a Hall IC 53 that faces the sensor magnet 52 inthe axial direction and serves as a magnetic sensor. When detecting amagnetic field of the N pole and a magnetic field of the S pole with thesensor magnet 52, the Hall IC 53 provides the control circuit S with adetection signal having an H level and a detection signal having an Llevel, respectively.

The operation of the first embodiment will now be described.

When the control circuit S supplies three-phase driving current to thecoils 8, the stator 5 generates a rotating magnetic field that drivesand rotates the rotor 11. Here, rotation of the sensor magnet 52, whichfaces the Hall IC 53, switches the level of the detection signal outputfrom the Hall IC 53, in accordance with the rotational angle (position)of the rotor 11. The control circuit S supplies, the coils 8 withthree-phase driving current switched at optimum timings in accordancewith the detection signal. This generates the rotating magnetic field ina desirable manner, and the rotor 11 is continuously rotated and drivenin a desirable manner.

As illustrated in FIGS. 2, 5, and 6, in the motor 1, the first andsecond rotor cores 15 and 16 of the rotor 11 are fixed to the commutatormagnet 18 by the adhesive 41. More specifically, the first core fixedsurface 22 c of the first claw pole 22 and the first magnet fixedsurface 31 a of the first back surface magnet portion 31 are fixed toeach other by the adhesive 41. Further, the second core fixed surface 24c of the second claw pole 24 and the second magnet fixed surface 32 a ofthe second back surface magnet portion 32 are fixed to each other by theadhesive 41.

When adhering and fixing the first core fixed surface 22 c and the firstmagnet fixed surface 31 a to each other, the adhesive 41 is applied tothe first core fixed surface 22 c. Then, the first core fixed surface 22c is bonded with the first magnet fixed surface 31 a. The first corefixed surface 22 c includes the first collection recess 22 d. Thisallows the adhesive 41 between the first core fixed surface 22 c and thefirst magnet fixed surface 31 a to enter the first collection recess 22d. The adhesive 41 may be applied to the first magnet fixed surface 31 aor to both of the first core fixed surface 22 c and the first magnetfixed surface 31 a.

In the same manner, when adhering and fixing the second core fixedsurface 24 c and the second magnet fixed surface 32 a to each other, theadhesive 41 is applied is to the second magnet fixed surface 32 a. Then,the second core fixed surface 24 c is bonded with the second magnetfixed surface 32 a. The second core fixed surface 24 c includes thesecond collection recess 24 d. This allows the adhesive 41 between thesecond core fixed surface 24 c and the second magnet fixed surface 32 ato enter the second collection recess 24 d. The adhesive 41 may beapplied to the second magnet fixed surface 32 a or to both of the secondcore fixed surface 24 c and the second magnet fixed surface 32 a.

When the adhesive 41 solidifies, the adhesive 41 fixes the first corefixed surface 22 c and the first magnet fixed surface 31 a to each otherand the second core fixed surface 24 c and the second magnet fixedsurface 32 a to each other. Thus, the adhesive 41 fixes the first andsecond rotor cores 15 and 16 to the commutator magnet 18.

The advantages of the first embodiment will now be described.

(1) The first and second rotor cores 15 and 16 are fixed to thecommutator magnet 18 by the adhesive 41, and the first core fixedsurface 22 c includes the first collection recess 22 d. Thus, when thefirst core fixed surface 22 c and the first magnet fixed surface 31 aare bonded and fixed to each other, the adhesive 41 between the firstcore fixed surface 22 c and the first magnet fixed surface 31 a isallowed to enter the first collection recess 22 d. The second core fixedsurface 24 c includes the second collection recess 24 d. Thus, when thesecond core fixed surface 24 c and the second magnet fixed surface 32 aare bonded and fixed to each other, the adhesive 41 between the secondcore fixed surface 24 c and the second magnet fixed surface 32 a isallowed to enter the second collection recess 24 d. This reduces leakageof the adhesive 41 from between the first core fixed surface 22 c andthe first magnet fixed surface 31 a that are fixed to each other andfrom between the second core fixed surface 24 c and the second magnetfixed surface 32 a that are fixed to each other. Thus, the adhesive 41applied to the first core fixed surface 22 c is more likely to remainbetween the first core fixed surface 22 c and the first magnet fixedsurface 31 a. Further, the adhesive 41 applied to the second core fixedsurface 24 c is more likely to remain between the second core fixedsurface 24 c and the second magnet fixed surface 32 a. This allows theadhesive 41 to be fixed by the commutator magnet 18 in a desirablemanner.

(2) The first collection recess 22 d and the second collection recess 24d are each simply shaped as a groove extending in the axial direction.This facilitates the formation of the first collection recess 22 d andthe second collection recess 24 d in the first core fixed surface 22 cand the second core fixed surface 24 c, respectively. The firstcollection recess 22 d extends from one end to the other end of thefirst core fixed surface 22 c in the axial direction. Thus, the adhesive41 is allowed to enter the first collection recess 22 d from any axialposition on the first core fixed surface 22 c. In the same manner, thesecond collection recess 24 d extends from one end to the other end ofthe second core fixed surface 24 c in the axial direction. Thus, theadhesive 41 is allowed to enter the second collection recess 24 d fromany axial position on the second core fixed surface 24 c. This reducesleakage of the adhesive 41 from between the first core fixed surface 22c and the first magnet fixed surface 31 a, which are fixed to eachother, and from between the second core fixed surface 24 c and thesecond magnet fixed surface 32 a, which are fixed to each other. Thus,the adhesive 41 applied to the first core fixed surface 22 c is furtherlikely to remain between the first core fixed surface 22 c and the firstmagnet fixed surface 31 a, and the adhesive 41 applied to the secondcore fixed surface 24 c is further likely to remain between the secondcore fixed surface 24 c and the second magnet fixed surface 32 a. Thisallows the commutator magnet 18 to be fixed by the adhesive 41 in adesirable manner.

(3) The adhesive 41 allows the commutator magnet 18 to be easily fixedto the first and second rotor cores 15 and 16.

Second Embodiment

A motor according to a second embodiment will now be described. In thesecond embodiment, same reference numerals are given to those componentsthat are the same as the corresponding components of the firstembodiment. Such components will not be described.

A rotor 61 of the second embodiment, illustrated in FIGS. 8 and 9A, isused instead of the rotor 11 of the first embodiment in the motor 1.

The rotor 61 includes a cylindrical fixed cylinder 62 fixed to therotation shaft 14, first and second rotor cores 63 and 64 that are fixedto the fixed cylinder 62, a field magnet 65 located between the firstand second rotor cores 63 and 64, and first and second back surfacemagnets 66 and 67 and first and second interpolar magnets 68 and 69 thatare located on an outer circumference of the field magnet 65.

The first rotor core 63, which is formed by a magnetic steel plate of asoft magnetic material, includes a disk-shaped first core base 71 and aplurality of (four in the present embodiment) first claw poles 72 thatare arranged in the circumferential direction on an outercircumferential portion of the first core base 71. A through hole 71 a,into which the fixed cylinder 62 is inserted and fixed, extends througha radially central portion of the first core base 71. The four firstclaw poles 72 are arranged at equal intervals (interval of 90°) in thecircumferential direction on the outer circumferential portion of thefirst core base 71.

The first claw poles 72 each include a first radially extending portion72 a, which extends outward in the radial direction from the outercircumferential portion of the first core base 71, and a first axiallyextending portion 72 b, which projects toward one axial side from adistal end (outer end in radial direction) of the first radiallyextending portion 72 a. The first radially extending portion 72 a has asectoral shape as viewed in the axial direction and widens in thecircumferential direction toward the outer side in the radial direction.The first axially extending portion 72 b has a sectoral cross-section ina direction orthogonal to the axial direction with a circumferentialwidth that increases in the radial direction. The radially outer surfaceof each first axially extending portion 72 b is arcuate and extendsabout the rotation axis of the rotor 61, as viewed in the axialdirection. The radially inner surfaces of the four first axiallyextending portions 72 b are arcuate and lie along the same circleextending about the rotation axis of the rotor 61, as viewed in theaxial direction. The two circumferential end surfaces of each first clawpole 72 define first core fixed surfaces 72 c fixed to a firstinterpolar magnet 68 or a second interpolar magnet 69 by an adhesive 41.Each of the first core fixed surfaces 72 c is planar and extends in theradial direction parallel to the axial direction. The first claw poles72 are each symmetrical in shape with respect to a plane that extendsthrough a circumferentially central portion and is orthogonal to thecircumferential direction.

The second rotor core 64, which is identical in shape to the first rotorcore 63, includes a second core base 81 and a plurality of (four in thepresent embodiment) second claw poles 82 that are arranged in thecircumferential direction on an outer circumferential portion of thesecond core base 81. The second core base 81 includes a through hole 81a, in which the fixed cylinder 62 is inserted and fixed, and isidentical in shape to the first core base 71 including the through hole71 a. Each of the second claw poles 82 includes a second radiallyextending portion 82 a and a second axially extending portion 82 b. Thesecond claw poles 82 are identical in shape to the first claw poles 72,each including the first radially extending portion 72 a and the firstaxially extending portion 72 b. The circumferential end surfaces of eachsecond claw pole 82 define second core fixed surfaces 82 c fixed to afirst interpolar magnet 68 or a second interpolar magnet 69 by theadhesive 41. Each of the second core fixed surfaces 82 c is planar andextends in the radial direction parallel to the axial direction like thefirst core fixed surface 72 c.

The fixed cylinder 62 is press-fitted in the through holes 71 a and 81 ato fix the first rotor core 63 and the second rotor core 64 to the fixedcylinder 62 with an interval maintained in between in the axialdirection. The fixed cylinder 62 is fitted and fixed to the outer sideof the rotation shaft 14. The first rotor core 63 and the second rotorcore 64 are fixed to the rotation shaft 14 by the fixed cylinder 62. Thefirst and second rotor cores 63 and 64 are fixed to the fixed cylinder62, and the field magnet 65 is held between the first rotor core 63 andthe second rotor core 64. The first rotor core 63 and the second rotorcore 64 are fixed to the fixed cylinder 62 stacked upon each other inthe axial direction, with distal ends of the first and second axiallyextending portions 72 b and 82 b thereof facing the directions oppositeto each other. The second claw poles 82 are located between the adjacentfirst claw poles 72 in the circumferential direction. The first axiallyextending portions 72 b and the second axially extending portions 82 bof the first and second rotor cores 63 and 64, which are fixed to thefixed cylinder 62, are alternately arranged in the circumferentialdirection at equal intervals (interval of 45°).

When the first and second rotor cores 63 and 64 are coupled to eachother, the first core base 71 and the second core base 81 are parallelto each other. Further, the field magnet 65 is located between the firstcore base 71 and the second core base 81. For example, the field magnet65 is a disk-shaped permanent magnet and formed by a neodymium magnet. Athrough hole 65 a, in which the fixed cylinder 62 is inserted, extendsthrough a radially central portion of the field magnet 65. The fieldmagnet 65 has one axial end surface (left end surface in FIG. 8) andanother axial end surface (a right surface in FIG. 8) that arerespectively in contact with the first core base 71 and the second corebase 81. The field magnet 65 is held and fixed between the first corebase 71 and the second core base 81. The field magnet 65 has the sameouter diameter as the core bases 71 and 81.

The field magnet 65 is magnetized in the axial direction so that thefirst claw pole 72 functions as the N pole and the second claw pole 82functions as the S pole. More specifically, the field magnet 65 ismagnetized in the axial direction so that a portion closer to the firstcore base 71 serves as the N pole and a portion closer to the secondcore base 81 serves as the S pole. Consequently, the first and secondclaw poles 72 and 82 function as different magnetic poles in thecircumferential direction. As described above, the rotor 61 in thepresent embodiment is a Lundell rotor that uses the field magnet 65. Therotor 61 includes the four first claw poles 72, each serving as the Npole, and the four second claw poles 82, each serving as the S pole,that are alternately arranged in the circumferential direction. Thus,the rotor 61 includes a total of eight poles (four magnetic pole pairs).

The first back surface magnets 66 are located between back surfaces 72 d(i.e., radially inner surfaces of first claw poles 72) of thecorresponding first claw poles 72 of the first rotor core 63 and anouter circumferential surface 81 b of the second core base 81 and anouter circumferential surface 65 b of the field magnet 65. The secondback surface magnets 67 are located between back surfaces 82 d (i.e.,radially inner surfaces of second claw poles 82) of the correspondingsecond claw poles 82 of the second rotor core 64 and the outercircumferential surface 71 b of the first core base 71 and the outercircumferential surface 65 b of the field magnet 65. Thus, in the rotor61, the first back surface magnets 66 are located at four positionsarranged at equal intervals (interval of 90°) in the circumferentialdirection. The second back surface magnets 67 are located betweenadjacent first back surface magnets 66 in the circumferential direction.The first back surface magnets 66 and the second back surface magnets 67are alternately arranged at intervals of 45° in the circumferentialdirection.

Each first back surface magnet 66 has a sectoral shape and a constantradial width as viewed in the axial direction. The radial width of thefirst back surface magnet 66 has substantially the same value as theinterval between the back surface 72 d of the first claw pole 72 and theouter circumferential surface 81 b of the second core base 81. Aradially outer surface of the first back surface magnet 66, which isarcuate and has substantially the same curvature as the back surface 72d of the first claw pole 72, is in contact with the back surface 72 d ofthe corresponding first claw pole 72. A radially inner surface of thefirst back surface magnet 66, which is arcuate and has substantially thesame curvature as the outer circumferential surface 81 b of the secondcore base 81, is in contact with the outer circumferential surface 81 bof the second core base 81 and the outer circumferential surface 65 b ofthe field magnet 65. The first back surface magnet 66 has an axiallength that is substantially the same as the sum of the axial lengths ofthe second core base 81 and the field magnet 65. The first back surfacemagnet 66 has one axial end surface (left end surface in FIG. 8) incontact with the first radially extending portion 72 a and another axialend surface (the right end surface in FIG. 8) positioned on the sameplane as a distal end surface of the first axially extending portion 72b in the axial direction. The first back surface magnet 66 hassubstantially the same circumferential width as the first radiallyextending portion 72 a. The first back surface magnet 66 has twocircumferential end surfaces defining first back surface magnet fixedsurfaces 66 a that are fixed to a first interpolar magnet 68 or a secondinterpolar magnet 69 by the adhesive 41. The first back surface magnetfixed surfaces 66 a are planar and extend in the radial directionparallel to the axial direction. The first back surface magnet fixedsurfaces 66 a defined by the two circumferential sides of the first backsurface magnet 66 are located on the same planes as the first core fixedsurfaces 72 c defined by the two circumferential ends of the first clawpole 72.

The first back surface magnet 66 is magnetized so that the part opposingthe back surface 72 d of the first claw pole 72 serves as the N pole,which is the same polarity as the first claw pole 72, and the part incontact with the outer circumferential surface 81 b of the second corebase 81 serves as the S pole, which is the same polarity as the secondcore base 81.

The second back surface magnets 67 are identical in shape to the firstback surface magnets 66. A radially outer surface of each of the secondback surface magnets 67 is in contact with the back surface 82 d of thecorresponding second claw pole 82. A radially inner surface of thesecond back surface magnets 67 is in contact with the outercircumferential surface 71 b of the first core base 71 and the outercircumferential surface 65 b of the field magnet 65. The second backsurface magnet 67 has one axial end surface (right end surface in FIG.8) in contact with the second radially extending portion 82 a andanother axial end surface (left end surface in FIG. 8) located on thesame plane as the distal end surface of the second axially extendingportion 82 b in the axial direction. The second back surface magnet 67has two circumferential end surfaces defining second back surface magnetfixed surfaces 67 a that are fixed to the first interpolar magnet 68 orthe second interpolar magnet 69 by the adhesive 41. The second backsurface magnet fixed surfaces 67 a at the two circumferential sides ofthe second back surface magnet 67 are located on the same planes as thesecond core fixed surfaces 82 c at the two circumferential ends of thecorresponding second claw pole 82.

The second back surface magnet 67 is magnetized so that the portionopposing the back surface 82 d of the second claw pole 82 serves as theS pole, which is the same polarity as the second claw pole 82, and theportion opposing the outer circumferential surface 71 b of the firstcore base 71 serves as the N pole, which is the same polarity as thefirst core base 71.

The first and second interpolar magnets 68 and 69 are each locatedbetween the first claw pole 72 and the second claw pole 82 that areadjacent in the circumferential direction.

The first interpolar magnet 68 is located between the first back surfacemagnet 66 and the second back surface magnet 67 that are adjacent in thecircumferential direction. Further, the first interpolar magnet 68 islocated between one first core fixed surface 72 c (clockwise end surfaceas viewed in FIG. 9A) of a first claw pole 72 and one second core fixedsurface 82 c (counterclockwise end surface as viewed in FIG. 9A) of asecond claw pole 82. The first interpolar magnet 68 is post-like and hasa sectoral cross-section orthogonal to the axial direction. The firstinterpolar magnet 68 has a circumferential width that is substantiallythe same as the interval between one first core fixed surface 72 c ofthe first claw pole 72 and one second core fixed surface 82 c of thesecond claw pole 82. The first interpolar magnet 68 has substantiallythe same radial width as the first claw pole 72. The first interpolarmagnet 68 has the same axial length as the first claw pole 72. Aradially outer surface of the first interpolar magnet 68 and radiallyouter surfaces of the first and second claw poles 72 and 82 lie alongthe same circle extending about the rotation axis of the rotor 61, asviewed in the axial direction.

As illustrated in FIG. 9B, the first interpolar magnet 68 has twocircumferential end surfaces defining first interpolar magnet fixedsurfaces 68 a fixed to the first back surface magnet 66 or the secondback surface magnet 67 by the adhesive 41. Each of the first interpolarmagnet fixed surfaces 68 a is planar and extends in the radial directionand parallel to the axial direction. Each of the first interpolar magnetfixed surface 68 a includes a first collection recess 68 b. The firstcollection recess 68 b is located in a radially central portion of thecorresponding first interpolar magnet fixed surface 68 a. Further, thefirst collection recess 68 b has the form of a groove extending in theaxial direction. The first collection recess 68 b extends over the firstinterpolar magnet fixed surface 68 a from one end to the other end of inthe axial direction. The first collection recess 68 b has a rectangularcross-sectional shape and a constant circumferential width. Thecross-sectional shape is uniform from one end to the other end of thefirst collection recess 68 b in the axial direction. The firstcollection recess 68 b is open at one circumferential side and two axialsides.

As illustrated in FIGS. 8 and 9A, the second interpolar magnet 69 isidentical in shape to the first interpolar magnet 68. The secondinterpolar magnet 69 is located between the first back surface magnet 66and the second back surface magnet 67 that are adjacent in thecircumferential direction. Further, the second interpolar magnet 69 islocated between the one first core fixed surface 72 c of the first clawpole 72 (counterclockwise end surface as viewed in FIG. 9A) and onesecond core fixed surface 82 c of the second claw pole 82(counterclockwise end surface as viewed in FIG. 9A). The secondinterpolar magnet 69 has two circumferential end surfaces definingsecond interpolar magnet fixed surfaces 69 a fixed to the first backsurface magnet 66 or the second back surface magnet 67 by the adhesive41. The second interpolar magnet fixed surface 69 a includes a secondcollection recess 69 b having the same shape as the first collectionrecess 68 b.

The first and second interpolar magnets 68 and 69 are magnetized in thecircumferential direction so that the opposing surfaces of the first andsecond claw poles 72 and 82 and the first and second interpolar magnets68 and 69 have the same polarity. More specifically, the first andsecond interpolar magnets 68 and 69 are magnetized in thecircumferential direction so that the portion closer to the first clawpole 72 serves as the N pole and the portion closer to the second clawpole 82 serves as the S pole.

The operation of the second embodiment will now be described.

As illustrated in FIGS. 9A and 9B, the four first back surface magnets66, the four second back surface magnets 67, the four first interpolarmagnets 68, and the four second interpolar magnets 69 are arranged onthe outer circumference of the field magnet 65 in an annular form as awhole surrounding the outer circumference of the field magnet 65.Circumferentially adjacent ones of the four first back surface magnets66, the four second back surface magnets 67, the four first interpolarmagnets 68, and the four second interpolar magnets 69 are fixed to eachother by the adhesive 41.

More specifically, the adhesive 41 fixes the first interpolar magnetfixed surface 68 a at the other circumferential side (distal end side incounterclockwise direction as viewed in FIG. 9) of the first interpolarmagnet 68 to the first back surface magnet fixed surface 66 a at onecircumferential side (distal end side in clockwise direction as viewedin FIG. 9) of the first back surface magnet 66 and the first core fixedsurface 72 c at one circumferential side (distal end side in clockwisedirection as viewed in FIG. 9) of the first claw pole 72. When adheringand fixing the first interpolar magnet 68 to the first back surfacemagnet 66 and the first claw pole 72, which are adjacent to the firstinterpolar magnet 68 in the circumferential direction, the adhesive 41is applied to the first interpolar magnet fixed surface 68 a. Theadhesive 41 may be applied to the first core fixed surface 72 c and thefirst back surface magnet fixed surface 66 a. Alternatively, theadhesive 41 may be applied to every one of the first interpolar magnetfixed surface 68 a, the first core fixed surface 72 c, and the firstback surface magnet fixed surface 66 a. Then, the first interpolarmagnet fixed surface 68 a is placed upon the first back surface magnetfixed surface 66 a and the first core fixed surface 72 c that oppose thefirst interpolar magnet fixed surface 68 a in the circumferentialdirection. The first interpolar magnet fixed surface 68 a includes thefirst collection recess 68 b. Thus, the adhesive 41 between the firstback surface magnet fixed surface 66 a and the first core fixed surface72 c and the first interpolar magnet fixed surface 68 a can enter thefirst collection recess 68 b. When the adhesive 41 solidifies, theadhesive 41 fixes the first interpolar magnet fixed surface 68 a to thefirst core fixed surface 72 c and the first back surface magnet fixedsurface 66 a, which are opposed to the first interpolar magnet fixedsurface 68 a in the circumferential direction. Thus, the adhesive 41fixes the first interpolar magnet 68 to the first back surface magnet 66and the first claw pole 72, which are arranged in the circumferentialdirection.

In the same manner, the adhesive 41 fixes the first interpolar magnetfixed surface 68 a at one circumferential side (distal end side inclockwise direction as viewed in FIG. 9) of the first interpolar magnet68 to the second back surface magnet fixed surface 67 a at the othercircumferential side (distal end side in counterclockwise direction asviewed in FIG. 9) of the second back surface magnet 67 and the secondcore fixed surface 82 c at the other circumferential side (distal end inthe counterclockwise direction in FIG. 9A) of the second claw pole 82.

In the same manner, the adhesive 41 fixes the second interpolar magnetfixed surface 69 a at one circumferential side (distal end side inclockwise direction as viewed in FIG. 9A) of the second interpolarmagnet 69 to the first back surface magnet fixed surface 66 a at theother circumferential side (distal end side in counterclockwisedirection as viewed in FIG. 9A) of the first back surface magnet 66 andthe first core fixed surface 72 c at the other circumferential side(distal end side in counterclockwise direction as viewed in FIG. 9A) ofthe first claw pole 72.

In the same manner, the adhesive 41 fixes the second interpolar magnetfixed surface 69 a at the other circumferential side (distal end side incounterclockwise direction as viewed in FIG. 9A) of the secondinterpolar magnet 69 to the second back surface magnet fixed surface 67a at one circumferential side (distal end side in clockwise direction asviewed in FIG. 9A) of the second back surface magnet 67 and second corefixed surfaces 82 c at one circumferential side (distal end side inclockwise direction as viewed in FIG. 9A) of the second claw pole 82.

The second embodiment has the following advantages in addition toadvantage (2) of the first embodiment.

(4) The adhesive 41 fixes the circumferentially adjacent ones of thefour first back surface magnets 66, the four second back surface magnets67, the four first interpolar magnets 68, and the four second interpolarmagnets 69. Each first interpolar magnet fixed surface 68 a includes thefirst collection recess 68 b. Thus, when the first interpolar magnetfixed surface 68 a is placed on and fixed to the first back surfacemagnet fixed surface 66 a and the first core fixed surface 72 c, theadhesive 41 located in between enters the first collection recess 68 b.When the first interpolar magnet fixed surface 68 a is placed on andfixed to the second back surface magnet fixed surface 67 a and thesecond core fixed surface 82 c, the adhesive 41 enters the firstcollection recess 68 b. In the same manner, each second interpolarmagnet fixed surface 69 a includes the second collection recess 69 b.Thus, when the second interpolar magnet fixed surface 69 a is placed onand fixed to the first back surface magnet fixed surface 66 a and thefirst core fixed surface 72 c, the adhesive 41 located in between entersthe second collection recess 69 b. When the second interpolar magnetfixed surface 69 a is placed on and fixed to the second back surfacemagnet fixed surface 67 a and the second core fixed surface 82 c, theadhesive 41 located in between enters the second collection recess 69 b.This limits the leakage of the adhesive 41 from between the firstinterpolar magnet fixed surface 68 a and the first back surface magnetfixed surface 66 a and the first core fixed surface 72 c that are fixedto each other and from between the first interpolar magnet fixed surface68 a and the second back surface magnet fixed surface 67 a and secondcore fixed surface 82 c that are fixed to each other. Further, leakageof the adhesive 41 from between the second interpolar magnet fixedsurface 69 a and the first back surface magnet fixed surface 66 a andfirst core fixed surface 72 c that are fixed to each other and frombetween the second interpolar magnet fixed surface 69 a and the secondback surface magnet fixed surface 67 a and second core fixed surface 82c that are fixed to each other. Thus, the adhesive 41 applied to thefirst interpolar magnet fixed surface 68 a is apt to remain between thefirst interpolar magnet fixed surface 68 a and the first back surfacemagnet fixed surfaces 66 a or the second back surface magnet fixedsurfaces 67 a opposed to each other in the circumferential direction andbetween the first interpolar magnet fixed surface 68 a and the firstcore fixed surface 72 c or the second core fixed surface 82 c opposed toeach other in the circumferential direction. Further, the adhesive 41applied to the second interpolar magnet fixed surface 69 a is apt toremain between the second interpolar magnet fixed surface 69 a and thefirst back surface magnet fixed surfaces 66 a or the second back surfacemagnet fixed surfaces 67 a opposed to each other in the circumferentialdirection, and between the second interpolar magnet fixed surface 69 aand the first core fixed surface 72 c or the second core fixed surface82 c opposed to each other in the circumferential direction. As aresult, the first and second back surface magnets 66 and 67 and thefirst and second interpolar magnets 68 and 69 are fixed in a desirablemanner by the adhesive 41.

(5) Further, the circumferentially adjacent ones of the first backsurface magnets 66, the second back surface magnets 67, the firstinterpolar magnets 68, and the second interpolar magnets 69 are easilyfixed to each other by the adhesive 41. The first and second interpolarmagnets 68 and 69 and the first and second rotor cores 63 and 64 areeasily fixed to each other by the adhesive 41.

The first and second embodiments may be modified as follows.

In the first embodiment, the first collection recess 22 d is in the formof a groove extending in the axial direction from one axial end to theother axial end of the first core fixed surface 22 c. However, the formof the first collection recess 22 d is not limited in such a manner. Forexample, the first collection recess 22 d may be shorter than the firstcore fixed surface 22 c in the axial direction. The first collectionrecess 22 d may have the form of a groove extending in thecircumferential direction in the first core fixed surface 22 c. The formof the first collection recess 22 d is not limited to a groove and maybe a semispherical, cubic, pyramidal, or conical recess. A plurality ofthe first collection recesses 22 d may be formed in each first corefixed surface 22 c. The same applies to the second collection recess 24d of the second core fixed surface 24 c.

The first collection recess 68 b and the second collection recess 69 bin the second embodiment are also not limited to the forms of the secondembodiment. For example, the first collection recess 68 b and the secondcollection recess 69 b may be a groove that is shorter than the firstinterpolar magnet fixed surface 68 a and the second interpolar magnetfixed surface 69 a in the axial direction or may be a groove extendingin the radial direction. The first collection recess 68 b and the secondcollection recess 69 b may be a semispherical, cubic, pyramidal, orconical recess. The first interpolar magnet fixed surface 68 a mayinclude a plurality of first collection recesses 68 b, and the secondinterpolar magnet fixed surface 69 a may include a plurality of secondcollection recesses 69 b.

As illustrated in FIG. 10, the first core fixed surface 22 c may includea first collection recess 101 instead of the first collection recess 22d in the first embodiment. The first collection recess 101 has the formof a groove that extends in the axial direction and opens at the side ofthe first magnet fixed surface 31 a (radially inner side as viewed inFIG. 10). The first collection recess 101 has an inner circumferentialsurface including inclined surfaces 101 a that extend continuously fromthe two circumferential ends of the first collection recess 101 in thefirst core fixed surface 22 c and are inclined relative to the firstcore fixed surface 22 c. The angle is obtuse between each inclinedsurfaces 101 a and the first core fixed surface 22 c where the firstcore fixed surface 22 c is fixed to the first magnet fixed surface 31 a.The inclined surfaces 101 a in the inner circumferential surface of thefirst collection recess 101 allows the adhesive 41 between the firstcore fixed surface 22 c and the first magnet fixed surface 31 a, whichare fixed to each other, to enter the first collection recess 101. Thisfurther limits the leakage of the adhesive 41 from between the firstcore fixed surface 22 c and the first magnet fixed surface 31 a, whichare fixed to each other. Thus, the adhesive 41 applied to the first corefixed surface 22 c or the first magnet fixed surface 31 a is apt toremain between the first core fixed surface 22 c and the first magnetfixed surface 31 a. This fixes the commutator magnet 18 in a furtherdesirable manner with the adhesive 41.

The same advantage may be obtained by forming the first collectionrecess 101 with two inclined surfaces 101 a so that the first collectionrecess 101 has a V-shaped cross-sectional in a direction orthogonal tothe axial direction and opens toward the first magnet fixed surface 31a. The inner circumferential surface of the first collection recess 101may be formed to have the inclined surfaces 101 a only on one of theends in the circumferential direction. The second collection recess 24 dof the second core fixed surface 24 c, may have the same shape as thefirst collection recess 101. The inner circumferential surface of thefirst collection recess 68 b in the second embodiment may be an inclinedsurface that extends continuously from the first interpolar magnet fixedsurface 68 a and is inclined relative to the first interpolar magnetfixed surface 68 a. In the same manner, the inner circumferentialsurface of the second collection recess 69 b of the second embodimentmay be an inclined surface that extends continuously from the secondinterpolar magnet fixed surface 69 a and is inclined relative to thesecond interpolar magnet fixed surface 69 a.

As illustrated in FIG. 11, the first core fixed surface 22 c may includea first collection recess 102 instead of the first collection recess 22d in the first embodiment. The first collection recess 102 has the formof a groove that extends in the axial direction and opens toward thefirst magnet fixed surface 31 a (radially inner side as viewed in FIG.11). The inner circumferential surface of the first collection recess102 is an arcuate surface 102 a that extends continuously from the firstcore fixed surface 22 c and is curved to be arcuate. The angle is obtusebetween the arcuate surface 102 a and the first core fixed surface 22 cwhere the first core fixed surface 22 c is fixed to the first magnetfixed surface 31 a. The arcuate surface 102 a in the innercircumferential surface of the first collection recess 102 allows theadhesive 41 between the first core fixed surface 22 c and the firstmagnet fixed surface 31 a, which are fixed to each other, to easilyenter the first collection recess 102. This limits the leakage of theadhesive 41 from between the first core fixed surface 22 c and the firstmagnet fixed surface 31 a, which are fixed to each other. Further, theadhesive 41 applied to the first core fixed surface 22 c or the firstmagnet fixed surface 31 a is further apt to remain between the firstcore fixed surface 22 c and the first magnet fixed surface 31 a, whichare fixed to each other. Thus, the commutator magnet 18 is fixed in afurther desirable manner by the adhesive 41.

The inner circumferential surface of the first collection recess 102 mayhave at least one circumferential end that extends continuously from thefirst core fixed surface 22 c and is curved in an arcuate manner. Inthis case, the angle is obtuse between the arcuate surface and the firstcore fixed surface 22 c where the first magnet fixed surface 31 a isfixed to the first core fixed surface 22 c. The second collection recess24 d of the second core fixed surface 24 c may have the same shape asthe first collection recess 102. The inner circumferential surface ofthe first collection recess 68 b in the second embodiment may be anarcuate surface that extends continuously from the first interpolarmagnet fixed surface 68 a and is curved to be arcuate. In the samemanner, the inner circumferential surface of the second collectionrecess 69 b in the second embodiment may be an arcuate surface thatextends continuously from the second interpolar magnet fixed surface 69a and is curved to be arcuate

In the first embodiment, the first rotor core 15 includes the firstcollection recess 22 d, and the second rotor core 16 includes the secondcollection recess 24 d. However, the commutator magnet 18 may include acollection recess. For example, as illustrated in FIG. 12, the firstmagnet fixed surface 31 a may include a collection recess 103 that hasthe same shape as the first collection recess 22 d in the firstembodiment and is open toward the first core fixed surface 22 c.

In the second embodiment, the first core fixed surface 72 c and thesecond core fixed surface 82 c may include a collection recess. Further,the first back surface magnet fixed surface 66 a and the second backsurface magnet fixed surface 67 a may include a collection recess.

In the rotor 61 of the second embodiment, the back surface 72 d of thefirst claw pole 72 may be fixed to the first back surface magnet 66 bythe adhesive 41. In this case, the back surface 72 d and the radiallyouter surface of the first back surface magnet 66 serve as fixedsurfaces that are fixed to each other by the adhesive 41. A collectionrecess is included in at least one of the back surface 72 d and theradially outer surface of the first back surface magnet 66. In the samemanner, the back surface 82 d of the second claw pole 82 may be fixed tothe second back surface magnet 67 by the adhesive 41. In this case, theback surface 82 d and the radially outer surface of the second backsurface magnet 67 serve as fixed surfaces fixed to each other by theadhesive 41. A collection recess is included in at least one of the backsurface 82 d and the radially outer surface of the second back surfacemagnet 67.

The location where the first and second rotor cores 15 and 16 are fixedto the commutator magnet 18 by the adhesive 41 is not limited to that ofthe first embodiment. For example, in an example illustrated in FIG. 13,the second claw pole 24 has one circumferential end surface (end surfacein counterclockwise direction as viewed in FIG. 13) that defines a fixedcore surface 111 a, fixed to the first interpolar magnet portion 33. Thefirst interpolar magnet portion 33 has the other circumferential endsurface (end surface in clockwise direction as viewed in FIG. 13) thatdefines a fixed magnet surface 112 a fixed to the fixed core surface 111a. The fixed core surface 111 a includes a collection recess 113 a thatis open toward the fixed magnet surface 112 a. The fixed core surface111 a and the fixed magnet surface 112 a are fixed to each other by theadhesive 41. The second claw pole 24 has another circumferential endsurface (end surface in the clockwise direction as viewed in FIG. 13)that defines a fixed core surface 111 b fixed to the second interpolarmagnet portion 34. The second interpolar magnet portion 34 has anothercircumferential end surface (end surface in the counterclockwisedirection as viewed in FIG. 13) that defines a fixed magnet surface 112b fixed to the fixed core surface 111 b. The fixed core surface 111 bincludes a collection recess 113 b that is open toward the fixed magnetsurface 112 b. The fixed core surface 111 b and the fixed magnet surface112 b are fixed to each other by the adhesive 41.

In the second embodiment, the first and second rotor cores 63 and 64 andthe first and second interpolar magnets 68 and 69 are fixed to eachother by the adhesive 41. However, the first and second rotor cores 63and 64 and the first and second interpolar magnets 68 and 69 do notnecessarily have to be fixed to each other. In such a case,circumferentially adjacent ones of the first and second back surfacemagnets 66 and 67 and the first and second interpolar magnets 68 and 69are fixed to each other by the adhesive 41. The first interpolar magnetfixed surface 68 a includes a first collection recess 68 b. Thus, whenthe first interpolar magnet fixed surface 68 a and the first backsurface magnet fixed surface 66 a are placed upon and fixed to eachother, the adhesive 41 in between enters the first collection recess 68b. When the first interpolar magnet fixed surface 68 a and the secondback surface magnet fixed surface 67 a are placed upon and fixed to eachother, the adhesive 41 can enter the first collection recess 68 b. Inthe same manner, the second interpolar magnet fixed surface 69 aincludes the second collection recess 69 b. Thus, when the secondinterpolar magnet fixed surface 69 a and the first back surface magnetfixed surface 66 a are placed upon and fixed to each other, the adhesive41 in between can enter the second collection recess 69 b. When thesecond interpolar magnet fixed surface 69 a and the second back surfacemagnet fixed surface 67 a are placed upon and fixed to each other, theadhesive 41 in between can enter the second collection recess 69 b. Thislimits leakage of the adhesive 41 from between the first interpolarmagnet fixed surface 68 a and the first back surface magnet fixedsurface 66 a, which are fixed to each other, and from between the firstinterpolar magnet fixed surface 68 a and the second back surface magnetfixed surface 67 a, which are fixed to each other. In the same manner,leakage of the adhesive 41 is limited from between the second interpolarmagnet fixed surface 69 a and the first back surface magnet fixedsurface 66 a, which are fixed to each other, and from between the secondinterpolar magnet fixed surface 69 a and the second back surface magnetfixed surface 67 a, which are fixed to each other. Thus, the adhesive 41is apt to remain between the first back surface magnet fixed surface 66a and the first interpolar magnet fixed surface 68 a, between the firstinterpolar magnet fixed surface 68 a and the second back surface magnetfixed surface 67 a, between the second interpolar magnet fixed surface69 a and the first back surface magnet fixed surface 66 a, and betweenthe second interpolar magnet fixed surface 69 a and the second backsurface magnet fixed surface 67 a. As a result, the first and secondback surface magnets 66 and 67 e and the first and second interpolarmagnets 68 and 69 are fixed to each other in a desirable manner by theadhesive 41.

In the first embodiment, the first rotor core 15 and the second rotorcore 16 are both fixed to the commutator magnet 18 by the adhesive 41.Alternatively, the adhesive 41 may fix only one of the first rotor core15 and the second rotor core 16 to the commutator magnet 18.

In the first embodiment, the first rotor core 15 includes the five firstclaw poles 22, and the second rotor core 16 includes the five secondclaw poles 24. However, there is no limit to the number of the clawpoles 22 and 24 in the first and second rotor cores 15 and 16 are thenumber may be changed when required. In such a case, the number of thefirst and second back surface magnet portions 31 and 32 and the numberof the first and second interpolar magnet portions 33 and 34 in thecommutator magnet 18 are changed in accordance with the number of theclaw poles 22 and 24.

In the same manner, in the second embodiment, the number of the firstclaw poles 72 in the first rotor core 63 and the number of the secondclaw poles 82 in the second rotor core 64 may be changed when required.In such a case, the numbers of the first and second back surface magnets66 and 67 and the numbers of the first and second interpolar magnets 68and 69 are changed in accordance with the numbers of the claw poles 72and 82. The rotor 61 does not necessarily have to include the first andsecond back surface magnets 66 and 67.

In the first embodiment, the rotor 11 includes only one pair of thefirst and second rotor cores 15 and 16. Alternatively, the rotor 11 mayinclude more than one pair of the first and second rotor cores 15 and16. In such a case, the field magnet 17 is located between the first andsecond core bases 21 and 23 in each pair of the first and second rotorcores 15 and 16, and the commutator magnet 18 is located on the outercircumference of each field magnet 17. The pairs of the first and secondrotor cores 15 and 16 are stacked upon each other in the axialdirection. In the same manner, the rotor 61 of the second embodiment mayinclude more than one pair of the first and second rotor cores 63 and64.

The first embodiment, the second embodiment, and each of the abovemodifications may be combined.

Third Embodiment

A motor according to a third embodiment will now be described withreference to FIGS. 14 to 18.

As illustrated in FIG. 14, a motor casing 212 of a brushless motor 211,serving as the motor, includes a yoke housing 213, which is cylindricaland has a closed end, and an end housing 214, which is a nonmagneticbody formed from an aluminum alloy and closes an opening of the yokehousing 213.

As illustrated in FIG. 14, a stator 216 is fixed to an innercircumferential surface of the yoke housing 213. The stator 216 includesa stator core 217 and coils 220. The stator core 217 includes aplurality of teeth 217 a extending inward in a radial direction. Thecoils 220 are wound around the teeth 217 a with an insulator 219arranged in between. The stator 216 generates a rotating magnetic fieldwhen the external control circuit S supplies driving current to thecoils 220.

As illustrated in FIG. 15, the stator core 217 in the present embodimentincludes twelve teeth 217 a arranged in the circumferential direction.Accordingly, twelve slots 217 b are also formed between adjacent ones ofthe teeth 217 a is 12.

As illustrated in FIG. 15, the teeth 217 a each include a windingportion 218 a and projections 218 b projecting from the radially innerend of the winding portion 218 a toward opposite sides in thecircumferential direction. Coils 220 of the U, V, and W phases are woundaround the winding portions 218 a through concentrated winding.

As illustrated in FIG. 14, a rotor 221 of the brushless motor 211includes a rotation shaft 222 and is located inside the stator 216. Therotation shaft 222 is rotationally supported about an axis L by bearings223 and 224 (ball bearings). The bearing 223 is supported by the centerof a bottom portion 213 a of the yoke housing 213, and the bearing 224is supported by the center of the end housing 214.

As illustrated in FIGS. 14 and 16, the rotor 221 includes first andsecond rotor cores 231 and 232, which are supported by (fixed to) therotation shaft 222, and an annular field magnet (disk magnet) 233. Therotation shaft 222 is press-fitted into the rotor 221 to maintain theinterval between the first and second rotor cores 231 and 232 in theaxial direction. The field magnet 233 (disk magnet) located between thefirst rotor core 231 and the second rotor core 232 in the axialdirection. The rotor 221 further includes back surface magnets 234 and235 and interpolar magnets 236 and 237.

More specifically, the first rotor core 231 includes a plurality of(four in the present embodiment) first claw poles 213 b arranged atequal intervals on an outer circumferential portion of the first corebase 231 a, which is substantially disk-shaped. The first claw poles 213b project outward in the radial direction and extend in the axialdirection.

The second rotor core 232, which is identical in shape to the firstrotor core 231, includes a plurality of second claw poles 232 b arrangedat equal intervals on an outer circumferential portion of the secondcore base 232 a, which is substantially disk-shaped. The second clawpoles 232 b project outward in the radial direction and extend in theaxial direction. The first and second rotor cores 231 and 232 havecenter holes into which the rotation shaft 222 is inserted andpress-fitted to that the first and second rotor cores 231 and 232 arefixed to (supported by) the rotation shaft 222. The second rotor core232 is coupled to the first rotor core 231 so that each second claw pole232 b is located between two first claw poles 213 b that are adjacent toeach other in the circumferential direction and so that the field magnet233 is located (held) between the first core base 231 a and the secondcore base 232 a in the axial direction, in which the first core base 231a and the second core base 232 a are opposed to each other.

The field magnet 233 is a ferrite magnet or a neodymium magnet. Thefield magnet 233 is annular shape and includes a center hole 233 a intowhich the rotation shaft 222 is inserted formed. The field magnet 233 ismagnetized in the axial direction so that each first claw pole 213 bfunctions as a first magnetic pole (the N pole in the presentembodiment) and each second claw pole 232 b functions as a secondmagnetic pole (the S pole in the present embodiment). Thus, the rotor221 in the present embodiment is a Lundell rotor that uses the fieldmagnet 233. The rotor 221 includes the four first claw poles 231 b, eachserving as the N pole, and the four second claw poles 232 b, eachserving as the S pole, that are alternately arranged in thecircumferential direction. Thus, the rotor 221 includes a total of eightpoles (four magnetic pole pairs). In the present embodiment, the numberof poles of the rotor 221 is set to “eight,” and the number of teeth 217a of the stator 216 is set to “twelve.”

The back surface magnet 234, serving as the commutator magnet, islocated between the back surface of each first claw pole 231 b (asurface on the inner side in the radial direction) and the outercircumferential surface of the second core base 232 a. The back surfacemagnet 234, which has a sectoral cross-section in a direction orthogonalto the axis, and is magnetized so that the portion in contact with theback surface of the first claw pole 231 b serves as the N pole, which isthe same polarity as the first claw pole 231 b, and the portion incontact with the outer circumferential surface of the second core base232 a serves as the S pole, which is the same polarity of the secondcore base 232 a. This limits magnetic flux leakage from these portions.

The back surface magnet 235 is located between the back surface of eachsecond claw pole 232 b (a surface on the inner side in the radialdirection) and the outer circumferential surface of the first core base231 a, like in the first claw pole 231 b. The back surface magnet 235,which has a sectoral cross-section in a direction orthogonal to theaxis, is magnetized so that the portion in contact with the back surfaceof the second claw pole 232 b serves as the S pole and the portion incontact with the outer circumferential surface of the first core base231 a serves as the N pole. This limits magnetic flux leakage from theseportions.

As illustrated in FIGS. 15 and 16, interpolar magnets 236 and 237 arelocated between the first claw poles 231 b and the second claw poles 232b in the circumferential direction (between the back surface magnets 234and the back surface magnets 235 in the circumferential direction). Theinterpolar magnets 236 and 237 are magnetized in the circumferentialdirection to limit magnetic flux leakage from these portions.

As illustrated in FIG. 14, the rotor 221 includes a sensor magnet 242held by a magnet holder 241 that is substantially disk-shaped. Morespecifically, the magnet holder 241 includes a disk portion 241 b, whichhas a boss 241 a formed at the center, and a cylindrical portion 241 c,which extends from an outer edge of the disk portion 241 b. The sensormagnet 242 is annular and adhered to the inner circumferential surfaceof the cylindrical portion 241 c and a surface of the disk portion 241b. The boss 241 a is fitted to the rotation shaft 222 to fix the magnetholder 241 to the rotation shaft 222.

The end housing 214 includes a Hall IC 243 that opposes the sensormagnet 242 in the axial direction and serves as a magnetic sensor. Whendetecting a magnetic field of the N pole and a magnetic field of the Spole of the sensor magnet 242, the Hall IC 243 sends a detection signalhaving an H level and a detection signal having an L level to thecontrol circuit S, respectively. The control circuit S supplies thedriving current to the coil 220 based on the detection signal.

The first and second claw poles 231 b and 232 b include protrusions 231c and 232 c protruding inward in the radial direction to restrict themovement of the back surface magnets 234 and 235 in the axial direction.The protrusions 231 c and 232 c are formed by arranging the back surfacemagnets 234 and 235 in the first and second rotor cores 231 and 232 andthen pressing the first and second claw poles 231 b and 232 b in theaxial direction.

More specifically, as illustrated in FIG. 17, the back surface magnet234 (235) includes a chamfered portion 234 a (235 a) at a locationcorresponding to the protrusion 231 c (232 c), that is, at the radiallyouter side of the axial end. The distal end of the first claw pole 231 b(second claw pole 232 b) includes the protrusion 231 c (232 c) thatprojects inward in the radial direction and contacts the chamferedportion 234 a. The protrusions 231 c and 232 c of the present embodimentare located within an axial range in which the first core base 231 a andthe second core base 232 a are located. The protrusion 231 c (232 c) inthe present embodiment is formed by deforming part of the distal end ofthe first claw pole 231 b (second claw pole 232 b) with a jig 245 wedgedin the axial direction (see FIG. 18B) into the distal end of the firstclaw pole 231 b (second claw pole 232 b) that has no protrusion 231 c(232 c) as illustrated in FIG. 18A. Thus, the protrusions 231 c and 232c hold and restrict axial movement of the back surface magnets 234 and235.

The operation of the brushless motor 211 will now be described.

When the control circuit S supplies three-phase driving current to thecoils 220, the stator 216 generates a rotating magnetic field thatdrives and rotates the rotor 221. Here, rotation of the sensor magnet242, which opposes the Hall IC 243, switches the level of the detectionsignal output from the Hall IC 243 in accordance with the rotationalangle (position) of the rotor 221. In response to the detection signal,the control circuit S supplies the coils 220 with the three-phasedriving current switched at optimum timings. This generates the rotatingmagnetic field in a desirable manner, and continuously rotates the rotor221 in a continuous manner.

The advantages of the third embodiment will now be described.

(6) The first and second claw poles 231 b and 232 b include theprotrusions 231 c and 232 c protruding inward in the radial direction torestrict axial movement of the back surface magnets 234 and 235.Compared with when, for example, restricting axial movement with only anadhesive for example, resistance to high temperatures is increased andthe back surface magnets 234 and 235 can be held more firmly. Anadhesive is not used as in the present embodiment. This allows the backsurface magnets 234 and 235 to be in close contact, minimizes themagnetic gap in between, and limits magnetic flux leakage from the backsurface magnets 234 and 235. Since the present embodiment does not usean adhesive, time is not used to dry the adhesive is required. Thisimproves the productivity.

(7) The chamfered portions 234 a and 235 a are formed on the backsurface magnets 234 and 235 at locations corresponding to theprotrusions 231 c and 232 c. This limits cracking of the back surfacemagnets 234 and 235.

(8) The protrusions 231 c and 232 c are located within an axial range inwhich the first core base 231 a and the second core base 232 a arearranged. Thus, the protrusions 231 c and 232 c do not protrude in theaxial direction, and such portions are not enlarged in the axialdirection.

The third embodiment may be modified as follows.

The back surface magnets 234 and 235 and the interpolar magnets 236 and237 in the third embodiment may be replaced with a polar anisotropicmagnet 253 as illustrated in FIG. 19. The polar anisotropic magnet 253serves as an annular commutator magnet including back surface magnetportions 251, which serve as the back surface magnets, and interpolarmagnet portions 252, which serve as the interpolar magnets, arealternately arranged (integrally formed). As schematically shown by thearrows in FIG. 19, the polar anisotropic magnet 253 is oriented from theouter circumferential surface of the back surface magnet portion 251 tothe outer circumferential surfaces of the back surface magnet portions251 that are adjacent in the circumferential direction. Thus, the polaranisotropic magnet 253 is magnetized so that leakage flux is reduced ateach of the back surface magnet portions 251 and the interpolar magnetportions 252. In this example, the back surface magnet portions 251include chamfered portions 251 a at locations corresponding to theprotrusions 231 c and 232 c like the embodiments described above. Inthis configuration, the back surface magnet portions 251 and theinterpolar magnet portions 252 are both firmly held by the protrusions231 c and 232 c.

In the third embodiment, the back surface magnets 234 and 235 includethe chamfered portions 234 a and 235 a. Instead, for example, asillustrated in FIGS. 20A and 20B, the chamfered portions 234 a and 235 amay be omitted. In this example, the first claw pole 231 b (second clawpole 232 b) has a distal end extending out of the axial range where thefirst core base 231 a and the second core base 232 a are arranged. Aprotrusion 231 d (232 d) is formed by partially deforming the distal endof the first claw pole 231 b (second claw pole 232 b) with a jig 245wedged into the distal end in the axial direction.

For example, as illustrated in FIGS. 21A and 21B, the entire distal endof the first claw pole 231 b (second claw pole 232 b) extending out ofthe axial range where the first core base 231 a and the second core base232 a are arranged may be bent (or crushed) with a jig 246 to form aprotrusion 231 e (232 e).

For example, as illustrated in FIGS. 22A and 22B, a slit 231 f (232 f)may be formed in advance in the distal end of the first claw pole 231 b(second claw pole 232 b) of the modification described above (see FIGS.20A and 20B), and the protrusion 231 d (232 d) may be formed by wedgingthe jig 245 into the slit 231 f (232 f).

For example, as illustrated in FIGS. 23A and 23B, the first claw pole231 b (second claw pole 232 b) may extend out of the axial range wherethe first core base 231 a and the second core base 232 a are arranged,and a jig 247 may be used to limit radial outward protrusion of thedistal end. In this state, a protrusion 231 g (232 g) may be formed bycrushing the distal end with a jig 248.

In the third embodiment, the protrusions 231 c and 232 c are formedentirely over the first and second claw poles 231 b and 232 b in thecircumferential direction. Instead, the protrusions 231 c and 232 c maybe formed on portions of the first and second claw poles 231 b and 232 bin the circumferential direction.

For example, as illustrated in FIG. 24, protrusions 231 h and 232 h maybe formed on the two circumferential ends of each of the first andsecond claw poles 231 b and 232 b. Alternatively, for example, asillustrated in FIG. 25, protrusions 231 j and 232 j may be formed onlyon central portions of the first and second claw poles 231 b and 232 bin the circumferential direction.

In the third embodiment, the back surface magnets 234 and 235 are heldby only the protrusions 231 c and 232 c. Instead, the back surfacemagnets 234 and 235 may be adhered to each by an adhesive.

The rotor in each of the third embodiment and the modifications of thethird embodiment includes the interpolar magnets 236 and 237. However,the interpolar magnets 236 and 237 may be omitted.

The protrusions 231 c and 232 c protrude inward in the radial directionin the third embodiment. However, the protrusions may protrude in thecircumferential direction as long as axial movement of the commutatormagnet that is either the back surface magnets 234 and 235 or theinterpolar magnets 236 and 237 can be restricted.

For example, a modification illustrated in FIGS. 26 and 27 may beemployed. In this example, the back surface magnets 234 and 235 and theinterpolar magnets 236 and 237 in the third embodiment are replaced withthe polar anisotropic magnet 253 that is an annular commutator magnet,in which the back surface magnet portions 251, serving as the backsurface magnets, and the interpolar magnet portions 252, serving as theinterpolar magnets, are alternately arranged in the circumferentialdirection (integrally formed) like in the modification described above(see FIG. 19). The chamfered portions 251 a in the modificationdescribed above (see FIG. 19) are not formed in the polar anisotropicmagnet 253 of this example. In this example, a cylindrical insulatingcollar 254 is arranged at the inner side of the field magnet 233(between the field magnet 233 and the rotation shaft 222).

As illustrated in FIG. 27B, the first and second claw poles 231 b and232 b include protrusions 231 k and 232 k projecting in thecircumferential direction to restrict axial movement of the interpolarmagnet portions 252 (and the polar anisotropic magnet 253 including theback surface magnet portions 251). More specifically, distal ends of thefirst and second claw poles 231 b and 232 b of this example extend outof the axial range where the first core base 231 a and the second corebase 232 a are arranged. Jigs 255 (see FIG. 27B) are wedged into thedistal ends of the first and second claw poles 231 b and 232 b that areless the protrusions 231 k and 232 k (see FIG. 27A) in the axialdirection to partially deform and extend the distal ends of the firstand second claw poles 231 b and 232 b outward in the circumferentialdirection. Thus, the protrusions 231 k and 232 k hold the interpolarmagnet portions 252 in the axial direction and restrict movement. As aresult, the back surface magnet portions 251 and the interpolar magnetportions 252 that are formed integrally as the polar anisotropic magnet253 are both firmly held by the protrusions 231 k and 232 k.

For example, as illustrated in FIGS. 28A and 28B, the protrusions 231 kand 232 k may be formed by wedging the jig 255 into slits 231 m and 232m formed in advance in the distal ends of the first and second clawpoles 231 b and 232 b of the modification described above (see FIGS. 27Aand 27B).

For example, a modification as illustrated in FIGS. 29A and 29B may beemployed. Protrusions 231 n and 232 n of this example are formed bywedging a jig 256 into an outer circumference of the first and secondclaw poles 231 b and 232 b (see FIG. 29A), which are less theprotrusions 231 n and 232 n, from the outer side in the radial direction(see FIG. 29B) so that the first and second claw poles 231 b and 232 bare partially deformed to extend outward in the circumferentialdirection. In this example, the protrusions 231 n and 232 n are formedby wedging the jig 256 into slits 231 p and 232 p (see FIG. 29A) formedin advance in the outer circumferential surfaces of the first and secondclaw poles 231 b and 232 b.

Thus, each of the interpolar magnet portions 252 is sandwiched (held)between the protrusions 231 n and 232 n in the circumferential directionso that axial movement is restricted. Thus, the back surface magnetportion 251 and the interpolar magnet portion 252, which are formedintegrally as the polar anisotropic magnet 253, are both firmly held bythe protrusions 231 n and 232 n.

In these examples (see FIGS. 26 to 29), the protrusions 231 k, 232 k,231 n, and 232 n restrict axial movement of the interpolar magnetportions 252. This, in turn, restricts axial movement of the backsurface magnet portions 251. Alternatively, the protrusions 231 k, 232k, 231 n, and 232 n may be used when the interpolar magnet portions 252are independent interpolar magnets. In such a case, axial movement ofthe back surface magnets and the interpolar magnets may be restricted byprotrusions protruding inward in the radial direction in addition toprotrusions protruding in the circumferential direction.

Chamfered portions may be formed in the interpolar magnet portions 252(interpolar magnets) at locations corresponding to the protrusions 231k, 232 k, 231 n, and 232 n protruding in the circumferential direction.This limits cracking of the interpolar magnet portions 252 (interpolarmagnets).

In the third embodiment, the present invention is embodied in thebrushless motor 211 in which the number of poles of the rotor 221 is setto “eight” and the number of the teeth 217 a of the stator 216 is set to“twelve.” The number of poles of the rotor 221 and the number of teeth217 a of the stator 216 may be changed. For example, the presentinvention may be implemented as a brushless motor in which the number ofpoles of the rotor 221 is set to “ten” and the number of the teeth 217 aof the stator 216 is set to “twelve.”

Technical concepts that can be acknowledged from the third embodimentand its modifications will now de described together with theiradvantages.

(I) A motor, wherein the protrusion is located in an axial range inwhich two core bases of the first and second rotor cores are arranged.

In this configuration, the protrusions are located within the axialrange in which the two core bases of the first and second rotor coresare arranged and thus do not protrude in the axial direction. Thus, suchportion is not enlarged in the axial direction.

(II) A motor, wherein the protrusion is formed by applying pressure tothe claw pole in an axial direction or a radial direction in a state inwhich the commutator magnet is arranged.

In this configuration, the protrusions are formed by applying pressureto the claw pole in the axial direction or the radial direction in astate in which the commutator magnet is arranged. This facilitates theformation of the protrusion that restricts axial movement of thecommutator magnet.

Fourth Embodiment

A brushless motor according to a fourth embodiment will now be describedwith reference to FIGS. 30 to 34.

As illustrated in FIG. 30, a brushless motor M serving as the motorincludes a stator 302, which is fixed to an inner circumferentialsurface of a motor casing 301. A rotor 304, which has a Lundellconfiguration, is fixed to a rotation shaft 303 and rotated integrallywith the rotation shaft 303. The rotation shaft 303 is a stainless shaftthat is a nonmagnetic body. Bearings (not shown) support the rotationshaft 303 rotationally relative to the motor casing 301.

The stator 302 includes a cylindrical stator core 310 having a shape.The outer circumferential surface of the stator core 310 is fixed to theinner side surface of the motor casing 301. A plurality of teeth 311,formed along the axial direction and arranged at an equal pitch in thecircumferential direction, are formed on the inner side of the statorcore 310 and extended inward in the radial direction. Each tooth 311 isT-shaped and has a radially inner side that defines an innercircumferential surface 311 a, which is an arcuate surface extending inthe axial direction. The inner circumferential surface 311 a isconcentric to an arc extending about the axis O of the rotation shaft303.

A slot 312 is formed between adjacent ones of the teeth 311 in thecircumferential direction. In the present embodiment, the number of theteeth 311 is twelve. The number of the slots 312 is the same as thenumber of the teeth 311 and is thus twelve. Three phase coils, namely, aU-phase coil 313 u, a V-phase coil 313 v, and a W-phase coil 313 w arewound in a concentrated winding around the twelve teeth 311 in the slots312. The coils are wound in order in the circumferential direction.

Three-phase power supply voltage is applied to the phase coils 313 u,313 v, and 313 w so that the stator 302 generates a rotating magneticfield and rotates the rotor 304, which is fixed to the rotation shaft303 at the inner side of the stator 302.

As illustrated in FIGS. 31 to 34, the rotor 304 includes first andsecond rotor cores 320 and 330 and an integrated permanent magnet 340.

The first rotor core 320 is formed of a soft magnetic material. In thepresent embodiment, the first rotor core 320 is formed by a magneticsteel plate and includes a first core base 321, which is substantiallydisk-shaped and has a boss 320 a. The rotation shaft 303 is press-fittedin the boss 320 a. A plurality of (four in the present embodiment) firstclaw poles 322 are formed at equal intervals on an outer circumferentialportion of the first core base 321. The first claw poles 322 areprojected outward in the radial direction and extended in the axialdirection.

The second rotor core 330 and the first rotor core 320 are formed fromthe same material and identical in shape. The second rotor core 330includes a second core base 331, which is substantially disk-shaped andhas a boss 330 a. The rotation shaft 303 is press-fitted in the boss 330a. A plurality of (four in the present embodiment) second claw poles 332are formed at equal intervals on an outer circumferential portion of thesecond core base 331. The second claw poles 332 are projected outward inthe radial direction and extended in the axial direction.

The rotation shaft 303 is press-fitted to the bosses 320 a and 330 a tofix the first and second rotor cores 320 and 330 to the rotation shaft303. The second rotor core 330 is coupled to the first rotor core 320 byarranging the second claw poles 332 between adjacent ones of the firstclaw poles 322 in the circumferential direction and arranging (holding)a field magnet (hereinafter, referred to as a field magnet main body341) of the integrated permanent magnet 340 between the first core base321 and the second core base 331 in the axial direction.

As illustrated in FIGS. 31, 33, and 34, the field magnet main body 341of the integrated permanent magnet 340 is disk-shaped and includes acenter hole. The field magnet main body 341 is magnetized in the axialdirection so that each first claw pole 322 functions as a first magneticpole (N pole in the present embodiment) and each second claw pole 332functions as a second magnetic pole (S pole in the present embodiment).The rotor 304 of the present embodiment is a Lundell rotor. The rotor304 includes the four first claw poles 322, serving as the N poles, andthe four second claw poles 332, serving as the S poles, alternatelyarranged in the circumferential direction. Thus, the rotor 304 includesa total of eight magnetic poles (four magnetic pole pairs). In thepresent embodiment, the number of poles of the rotor 304 is set to“eight,” and the number of teeth 311 (slots 312) of the stator 302 isset to “twelve.”

The integrated permanent magnet 340 is obtained by integrally formingthe field magnet main body 341, back surface magnet portions 342, andinterpolar magnet portions 343. The back surface magnet portions 342,which are located between the field magnet main body 341 and the firstand second claw poles 322 and 332, are magnetized to limit magnetic fluxleakage from where the back surface magnet portions 342 are located. Theinterpolar magnet portions 343 are located between adjacent ones of theback surface magnet portions 342 in the circumferential direction andmagnetized to limit magnetic flux leakage from where the interpolarmagnet portions 343 are located (between the first and second claw poles322 and 332).

More specifically, the back surface magnet portions 342 and theinterpolar magnet portions 343 are alternately arranged at the radiallyouter side of the field magnet main body 341 in an annular form. Theback surface magnet portions 342 and the interpolar magnet portions 343are oriented from the outer circumferential surface of the back surfacemagnet portion 342 to the outer circumferential surfaces of the adjacentback surface magnet portion 342 in the circumferential direction asschematically indicated by the arrows in FIGS. 33 and 34. Further, theback surface magnet portions 342 and the interpolar magnet portions 343are magnetized so that each of the back surface magnet portions 342 andthe interpolar magnet portions 343 reduces leakage fluxes. The backsurface magnet portions 342 and the interpolar magnet portions 343 aremagnetized by large currents flowing through the coils near the outercircumferential surface of each back surface magnet portion 342. Thus,the back surface magnet portions 342 are mainly magnetized in the radialdirection, and the interpolar magnet portions 343 are mainly magnetizedin the circumferential direction. In FIGS. 33 and 34, the double-dashedline schematically indicates the boundary of the field magnet main body341 with the back surface magnet portions 342 and the interpolar magnetportions 343.

The back surface magnet portions 342 and the interpolar magnet portions343 are formed within an axial range that is the same as the axial rangein which the field magnet main body 341 is formed. More specifically, inthe integrated permanent magnet 340 of the present embodiment, eachaxial end surface is entirely flat. The axial end surface includes theboundary of the field magnet main body 341 with the back surface magnetportions 342 and the interpolar magnet portions 343. The outercircumference of the integrated permanent magnet 340 is circular andextends along radially inner end surfaces of the first and second clawpoles 322 and 332.

The operation of the brushless motor M will now be described.

When three-phase power supply voltage is applied to the phase coils 313u, 313 v, and 313 w of the stator core 310, the stator 302 generates arotating magnetic field. The rotating magnetic field rotates and drivesthe rotor 304, which is fixed to the rotation shaft 303 located at theinner side of the stator 302.

The back surface magnet portions 342 limit magnetic flux leakage atwhere the back surface magnet portions 342 are located (in the radialdirection) and the interpolar magnet portion 343 limit magnetic fluxleakage at where the interpolar magnet portion 343 are located (in thecircumferential direction). Thus, the rotating magnetic field of thestator 302 acts with highly efficiency to drive and rotate the rotor304.

The advantages of the fourth embodiment will now be described.

(9) The field magnet main body 341, the back surface magnet portions342, and the interpolar magnet portions 343 are formed integrally toform the integrated permanent magnet 340. This achieves high efficiencywithout increasing the number of components. The back surface magnetportions 342 and the interpolar magnet portions 343 are formed withinthe same axial range as the axial range in which the field magnet mainbody 341 is formed. This facilitates the formation of the integratedpermanent magnet 340 as compared when there is a portion projecting inthe axial direction from the axial range where the field magnet mainbody 341 is formed. As a result, the rotor 304 and the brushless motor Mmay be easily manufactured.

(10) Each axial end surface of the integrated permanent magnet 340 is asingle flat surface including the boundary of the field magnet main body341 with the back surface magnet portions 342 and the interpolar magnet343. This facilitates the formation as compared with when the boundaryincludes a groove.

(11) The outer circumference of the integrated permanent magnet 340 iscircular and extends along the radially inner end surfaces of the firstand second claw poles 322 and 332. This facilitates formation of theintegrated permanent magnet 340 as compared with when parts of theinterpolar magnet portions 343 project outward in the radial direction.

The fourth embodiment may be modified as described below.

In the fourth embodiment, the outer circumference of the integratedpermanent magnet 340 is circular and extends along the radially innerend surfaces of the first and second claw poles 322 and 332. Instead, asillustrated in FIG. 35, the interpolar magnet portions 343 may eachinclude an interpolar projection 343 a projecting outward in the radialdirection from the radially outer end surfaces of the back surfacemagnet portion 342. This further reduces magnetic flux leakage ascompared with when there are no interpolar projections 343 a (in theembodiment described above).

In the fourth embodiment, each axial end surface of the integratedpermanent magnet 340 is a single flat surface including the boundary ofthe field magnet main body 341 with the back surface magnet portions 342and the interpolar magnet portions 343. Instead, as illustrated in FIGS.36A and 36B, the boundary may include a groove 344. This increases theaccuracy of the magnetizing direction when magnetized. Morespecifically, it is desirable that the field magnet main body 341 bemagnetized in the axial direction, the back surface magnet portions 342be magnetized in the radial direction, and the interpolar magnetportions 343 be magnetized in the circumferential direction. Whenmagnetized, it is difficult for the magnetic flux to extend beyond theportion where the groove 344 is formed and into a range beyond themagnetizing range. This acts to more easily obtain the desiredmagnetization directions.

In the fourth embodiment, although not particularly mentioned, thematerial type and manufacturing method of the integrated permanentmagnet 340 are not particularly limited, and various types of magnetsmay be used. For example, a ferrite magnet, a samarium-iron-nitrogenbased magnet, a samarium-cobalt based magnet, a neodymium magnet, or analnico magnet may be used. A sintered magnet or a bonded magnet may beused. When a bonded magnet is used, compression molding or injectionmolding may be employed.

In the fourth embodiment, the present invention is embodied in thebrushless motor M in which the number of poles of the rotor 304 is setto “eight,” and the number of the teeth 311 of the stator 216 is set to“twelve.” However, the number of poles of the rotor 304 and the numberof teeth 311 of the stator 302 may be changed. For example, the presentinvention may be embodied in a brushless motor in which the number ofpoles of the rotor 304 is set to “ten,” and the number of the teeth 311of the stator 302 is set to “twelve.”

Technical concepts that can be recognized from the fourth embodiment andits modifications will now be described together with their advantages.

(III) A motor, wherein the integrated permanent magnet includes an axialend surface that entirely forms a single flat surface including aboundary of the field magnet main body with the back surface magnetportion and the interpolar magnet portion.

In this configuration, the integrated permanent magnet includes an axialend surface that entirely forms a single flat surface including aboundary of the field magnet main body with the back surface magnetportion and the interpolar magnet portion. This facilitates theformation as compared with when the boundary includes a groove, forexample.

(IV) In the motor, the interpolar magnet portions each include aninterpolar protrusion projecting outward in the radial direction beyondend surfaces of the back surface magnet portion on an outer side in theradial direction.

In this configuration, the interpolar magnet portions each include aninterpolar protrusion projecting outward in the radial direction beyondend surfaces of the back surface magnet portion on the outer side in theradial direction. Thus, the magnetic flux can be more effectivelyprevented from leaking compared with a configuration without theinterpolar protrusion.

Fifth Embodiment

A motor according to a fifth embodiment will now be described withreference to FIGS. 37 and 38.

As illustrated in FIG. 37, a rotation shaft 422 of the presentembodiment is formed by a magnetic body of iron. The rotation shaft 422includes a demagnetized portion 422 a, which undergoes a demagnetizationprocess to increase the magnetic resistance between a through hole 431 cof a first rotor core 431 and a through hole 432 c of a second rotorcore 432.

More specifically, in the present embodiment, the demagnetized portion422 a is located at an axial position including a range extending fromthe end of the through hole 431 c in the first rotor core 431 oppositeto a field magnet 433 (end facing away from the field magnet 433) andthe end of the through hole 432 c in the second rotor core 432 oppositeto the field magnet 433 (end facing away from the field magnet 433).Thus, in the present embodiment, the demagnetized portion 422 a islocated at an axial position in a range slightly larger than a rangebetween the two axial ends of the first and second rotor cores 431 and432, which are arranged on opposite sides of the field magnet 433. Thedemagnetizing process in the present embodiment includes applying aliquid containing nitrogen and executing high-temperature heating (laserradiation) so that nitrogen sinks in.

The operation of a brushless motor 411 having the configuration will nowbe described.

When the control circuit S supplies three-phase driving current to thecoils 420, the stator 416 generates a rotating magnetic field to rotateand drive the rotor 421. This rotates a sensor magnet 42, which isopposed to a Hall IC 443, and switches the level of the detection signaloutput from the Hall IC 443 in accordance with the rotational angle(position) of the rotor 421. In response to the detection signal, thecontrol circuit S supplies the coils 420 with three-phase drivingcurrent switched at optimum timings. Thus, the rotating magnetic fieldis generated in a desirable manner, and the rotor 421 is continuouslyrotated and driven in a desirable manner.

The advantages of the fifth embodiment will now be described.

(12) The rotation shaft 422 includes the demagnetized portion 422 a thatundergoes the demagnetizing process to obtain a higher magneticresistance between the through hole 431 c in the first rotor core 431and the through hole 432 c in the second rotor core 432. Thus, forexample, the magnetic flux leakage can be reduced at the portiondescribed above without using a rotation shaft that is entirely formedfrom a nonmagnetic metal material (for example, stainless steel). Forexample, when the rotation shaft is formed from iron like in the presentembodiment, the rotation shaft 422 has high rigidity. Further, costs arelowered in comparison to when the rotation shaft is formed fromstainless steel or the like.

(13) The demagnetized portion 422 a is located at an axial positionincluding the range from the end of the through hole 431 c in the firstrotor core 431 at the side opposite to the field magnet 433 and the endof the through hole 432 c in the second rotor core 432 at the sideopposite to the field magnet 433. This limits magnetic flux leakage witha simple configuration (range).

The fifth embodiment may be modified as described below.

In the fifth embodiment, the demagnetized portion 422 a is located atthe axial position including the range from the end of the through hole431 c in the first rotor core 431 at the side opposite to the fieldmagnet 433 and the end and the end of the through hole 432 c in thesecond rotor core 432 at the side opposite to the field magnet 433.Instead, the demagnetized portion 422 a may be located only at axialpositions corresponding to the through holes 431 c and 432 c. Thisobtains advantage (11) of the fifth embodiment.

The rotation shaft 422 in the fifth embodiment may be replaced with arotation shaft including a recess to obtain a higher magnetic resistancebetween the through hole 431 c in the first rotor core 431 and thethrough hole 432 c in the second rotor core 432.

For example, as illustrated in FIG. 38, a rotation shaft 451 may includea recess 451 a at (only) an axial position corresponding to the fieldmagnet 433 (through hole 433 a). The recess 451 a of this example has auniform depth and extends throughout the entire outer circumference ofthe rotation shaft 451 at the axial position of the rotation shaft 451corresponding to the field magnet 433.

This configuration also reduces magnetic flux leakage from between thethrough hole 431 c in the first rotor core 431 and the through hole 432c in the second rotor core 432 without using, for example, a rotationshaft entirely formed from a nonmagnetic metal material (for example,stainless steel). For example, when the rotation shaft is made of ironor the like, the rotation shaft 451 has high rigidity and reduces costsas compared to a rotation shaft formed from stainless steel or the like.

The recess 451 a is formed only at the axial position corresponding tothe field magnet 433. Thus, the magnetic flux leakage may be reducedwithout changing the configuration in which the rotation shaft 451 issupported by the through holes 431 c and 432 c in the first and secondrotor cores 431 and 432 while maintaining the supporting force.

Sixth Embodiment

A motor according to a sixth embodiment will now be described.

As illustrated in FIG. 39, a motor casing 512 of a brushless motor 511,which serves as the motor, includes a yoke housing 513, which iscylindrical and has a closed end, and an end plate 514, which closes anopening at a front side (left side in FIG. 39) of the yoke housing 513.

As illustrated in FIG. 39, a stator 516 is fixed to an innercircumferential surface of the yoke housing 513. The stator 516 includesa stator core 517 including a plurality of teeth 517 a, which extendinward in a radial direction, and coils 519, which are wound around theteeth 517 a with an insulator 518 arranged in between. The stator 516generates a rotating magnetic field when the external control circuit Ssupplies driving current to the coil 519.

As illustrated in FIG. 39, a rotor 521 of the brushless motor 511includes a rotation shaft 522 and is located at an inner side of thestator 516. The rotation shaft 522 is a metal shaft that is anonmagnetic body and is rotationally supported by bearings 523 and 524,which are supported by a bottom portion 513 a of the yoke housing 513and the end plate 514.

As illustrated in FIGS. 40 to 42, the rotor 521 includes two rotor cores531 and 541 and a field magnet 551. The rotor cores 531 and 541 arepress-fitted to the rotor 521. This fixes the rotor cores 531 and 541 tothe rotation shaft 522 with an interval maintained in between in theaxial direction. The field magnet 551 is annular and located between therotor cores 531 and 541 in the axial direction.

As illustrated in FIGS. 40 and 41, the rotor core 531 has a plurality of(five in the present embodiment) claw poles 536 that are arranged atequal intervals in the circumferential direction on an outercircumferential portion of the core base 532, which is substantiallydisk-shaped. The claw poles 536 project outward in the radial directionand extend in the axial direction.

The core base 532 is obtained by integrally forming an inner core base533, an intermediate core base 534 located at the outer side of theinner core base 533, and an outer core base 535 located at the outerside of the intermediate core base 534. The inner core base 533 and theouter core base 535 may be formed by a magnetic body of iron, forexample. The intermediate core base 534 is formed by a nonmagnetic body,for example. Thus, for example, the intermediate core base 534 has aweaker magnetic property (for example, magnetic permeability) than theinner core base 533 and the outer core base 535.

The claw pole 536 includes a radially extending portion 537, whichprojects outward in the radial direction from the outer circumferentialportion of the core base 532 (outer core base 535), and an axiallyextending portion 538, which is located on the distal end of theradially extending portion 537 and extends in the axial direction. Theradially extending portion 537 is substantially sectoral as viewed inthe axial direction. The axially extending portion 538 has a sectoralcross-section extending in a direction orthogonal to the axis. The clawpole 536 is formed by a magnetic body and may be formed from iron, forexample, like the inner core base 533 and the outer core base 535.

As illustrated in FIG. 40, the rotor core 541, which has substantiallythe same shape as the rotor core 531, includes a plurality of (five inthe present embodiment) claw poles 546 that are arranged at equalintervals in the circumferential direction on an outer circumferentialportion of the core base 542, which is substantially disk-shape. Theclaw poles 546 project outward in the radial direction and extend in theaxial direction.

The core base 542 is formed by integrally forming an inner core base543, an intermediate core base 544 located at the outer side of theinner core base 543, and an outer core base 545 located at the outerside of the intermediate core base 544. The inner core base 543 and theouter core base 545 are formed by a magnetic body of iron, for example.The intermediate core base 544 is formed by a nonmagnetic body, forexample. Thus, for example, the intermediate core base 544 has a weakermagnetic property (for example, magnetic permeability) than the innercore base 543 and the outer core base 545.

The claw pole 546 includes a radially extending portion 547, whichprojects outward in the radial direction from the outer circumferentialportion of the core base 542 (outer core base 545), and an axiallyextending portion 548, which is located on the distal end of theradially extending portion 547 and extends in the axial direction. Theradially extending portion 547 is substantially sectoral as viewed inthe axial direction. The axially extending portion 548 has a sectoralcross-section extending in a direction orthogonal to the axis. The clawpole 546 is formed by a magnetic body of iron, for example, like theinner core base 543 and the outer core base 545.

As illustrated in FIGS. 40 to 42, the field magnet 551 includes a diskportion 552 and radially extending portions 553. The disk portion 552has a larger diameter than the core bases 532 and 542 of the rotor cores531 and 541. More specifically, the diameter of the disk portion 552 isequal to the sum of the diameter of the core bases 532 and 542 theradial length of the radially extending portions 537 and 547. Thus, whenthe field magnet 551 is held between the rotor cores 531 and 541, innersurfaces 538 a and 548 a of the axially extending portions 538 and 548of the claw poles 536 and 546 are in contact with the disk portion 552in the radial direction. The radially extending portions 553 are locatedbetween the axially extending portions 538 of the claw pole 536 and theaxially extending portions 548 of the claw pole 546 in thecircumferential direction.

As illustrated in FIG. 42, the field magnet 551 has a substantiallyuniform length (thickness) in the axial direction. The field magnet 551is shorter than the claw poles 536 and 546 (axially extending portions538 and 548) of the rotor cores 531 and 541 in the axial direction.

As illustrated in FIGS. 40 and 42, the field magnet 551 isanisotropically oriented so that the claw poles 536 (axially extendingportions 538) of the rotor core 531, which are in contact with the fieldmagnet 551, function as S poles and the claw poles 546 (axiallyextending portions 548) of the rotor core 541, which are in contact withthe field magnet 551, function as the N poles. This forms magnetic polesthat change alternately in the circumferential direction. Thus, therotor core 531 and the rotor core 541 have different magnetic poles. Thenumber of the claw poles 536 is five and the number of the claw poles546 is five as described above. Thus, the field magnet 551 obtains tenpoles (five magnetic pole pairs).

As illustrated in FIG. 39, the rotor 521 includes a sensor magnet 562held by a magnet holder 561 that is substantially disk-shaped. Morespecifically, the magnet holder 561 includes a disk portion 561 b and acylindrical portion 561 c. A boss 561 a is formed at the center of thedisk portion 561 b. The cylindrical portion 561 c extends from an outeredge of the disk portion 561 b. The sensor magnet 562 is annular andfixed to an inner circumferential surface of the cylindrical portion 561c and a surface of the disk portion 561 b. The boss 561 a is fitted tothe rotation shaft 522 to fix the magnet holder 561 to the rotationshaft 522 near the rotor core 531.

The end plate 514 includes a Hall IC 563 that opposes the sensor magnet562 in the axial direction and serves as a magnetic sensor. The Hall IC563 outputs a detection signal having an H level and a detection signalhaving an L level to the control circuit S respectively when a magneticfield of the N pole and a magnetic field of the S pole are detected fromthe sensor magnet 562.

The operation of the brushless motor 511 will now be described.

When the control circuit S supplies three-phase driving current to thecoil 519, the stator 516 generates a rotating magnetic field to rotateand drive the rotor 521. Rotation of the sensor magnet 562, whichopposes the Hall IC 563, switches the level of the detection signaloutput from the Hall IC 563 in accordance with the rotational angle(position) of the rotor 521. In response to the detection signal, thecontrol circuit S supplies the coil 519 with three-phase driving currentswitched at optimum timings. Thus, the rotating magnetic field isgenerated in a desirable manner, and the rotor 521 is continuous rotatedand driven in a desirable manner.

In the rotor 521 of the present embodiment, the field magnet 551, whichis a single anisotropically oriented magnet, acts so that the claw poles536 and 546 of the rotor cores 531 and 541 function as differentmagnetic poles in the circumferential direction.

Next, the advantages of the sixth embodiment will be described.

(14) The field magnet 551, which is anisotropically oriented, acts sothat the claw poles 536 and 546 arranged in the circumferentialdirection function as different magnetic poles in the circumferentialdirection. Thus, with the single field magnet 551, the claw poles 536and 546 to function as different magnetic poles. This improves thecoupling efficiency without increasing the number of components.

(15) The field magnet 551 is anisotropically oriented. Thus, magneticflux is more concentrated than radial orientation. This allows for anincrease in the output of the motor 511.

(16) The rotor cores 531 and 541 used by different magnetic poles areseparate from each other. This reduces magnetic flux leakage andshort-circuiting flux that extend through the claw poles 536 and 546 andthe core bases 532 and 542 between different magnetic poles. This allowsfor an increase in the output of the motor 511.

(17) The core bases 532 and 542 at least partially include theintermediate core bases 534 and 544 that have a weaker magnetic propertythan the claw poles 536 and 546. This reduces short-circuiting flux inwhich the magnetic flux of the field magnet 551 acts to extend throughthe core bases 532 and 542 can be prevented. This allows for an increasein the output of the motor 511.

(18) The annular intermediate core bases 534 and 544 are provided forthe core bases 532 and 542. This further ensures reduction ofshort-circuiting flux in which the magnetic flux of the field magnet 551acts to extend through the core bases 532 and 542.

The sixth embodiment may be modified as described below.

The intermediate core bases 534 and 544 are formed by nonmagnetic bodiesin the sixth embodiment but may be formed by magnetic bodies as long asthe magnetic property is weaker than the claw poles 536 and the clawpole 546.

In the sixth embodiment, the field magnet 551 includes the intermediatecore bases 534 and 544 having a weaker magnetic property than the clawpoles 536 and the claw poles 546. However, the field magnet 551 may beformed by a member having the same magnetic property as the claw poles536 and the claw poles 546.

Further, the core bases 532 and 542 may be formed by members having aweaker magnetic property than the claw poles 536 and the claw poles 546.

For example, as illustrated in FIGS. 43 and 44, the axially extendingportions 538 and 548 of the claw poles 536 and 546 may include grooves538 b and 548 b recessed in the radial direction and extending in theaxial direction. In FIG. 44, the two grooves 538 b are formed in theaxially extending portions 538 and the two grooves 548 b are formed inthe axially extending portions 548 although this configuration may bechanged as required.

Instead of the grooves, slits may extend in the radial direction throughthe axially extending portions and extend in the axial direction. Theformation of grooves and slits allows the magnetic flux distribution tobe changed (adjusted). Thus, cogging torque and torque ripple can beadjusted, and rotor vibration can be decreased.

In the sixth embodiment, the field magnet 551 includes the disk portion552 and the radially extending portions 553. Instead, for example, asillustrated in FIGS. 45 to 47, the field magnet 551 may include only thedisk portion 552. When the field magnet 551 includes only the diskportion 552, the shape of the field magnet 551 is simplified.

In the sixth embodiment, the two rotor cores 531 and 541 are used.Instead, for example, there may be only one rotor core. In such a case,the claw poles 536 of the rotor core 531 and the claw poles 546 of therotor core 541 are formed on one of the rotor cores. This allows rotorto have the same number of poles as the rotor of the above embodimentwhen the same field magnet 551 is used.

The number of poles obtained with the field magnet 551 and the clawpoles 536 and 546 is ten in the sixth embodiment but may be changed whenrequired.

The sixth embodiment and its modifications may be combined as required.

Seventh Embodiment

A motor according to a seventh embodiment will now be described.

As illustrated in FIG. 48, a motor 610 of the present embodimentincludes a stator 611, which is annular is fixed to a motor housing (notshown), and a rotatable rotor 612, which is located at the inner side ofthe stator 611.

[Configuration of Stator]

The stator 611 includes a cylindrical stator core 613 and coils 614wound around the stator core 613. The stator core 613 includes an outercircumferential annular portion 615, which is fixed to the motorhousing, and a plurality of teeth 616, which extend inward in the radialdirection from the outer circumferential annular portion 615. The teeth616 are arranged at equal intervals in the circumferential direction.

Teeth 616

Each tooth 616 is T-shaped and has a radial distal end (radially innerend) in the radial direction that is wide in the circumferentialdirection. The tooth 616 includes a winding portion 617, around which acoil 614 is wound, and a distal tooth end 618, which is defined by theinner circumferential side of the winding portion 617. The windingportion 617 extends inward in the radial direction from the outercircumferential annular portion 615. The distal tooth end 618 is widerthan the winding portion 617 in the circumferential direction. An innercircumferential surface 618 a of the distal tooth end 618 (inner sidesurface in the radial direction) is an arcuate surface formed by axiallyextending an arc, with extends about the axis L of a rotation shaft 619of a rotor 612. The distal tooth end 618 has two flat axial end surfaces(first axial end surface 618 b and second axial end surface 618 c) thatare orthogonal to the axis L of the rotation shaft 619.

Configuration of Rotor

As illustrated in FIG. 49, the rotor 612 is provided with a first rotorcore 620, which includes a first main core 621 and a first auxiliarycore 622, a second rotor core 630, which includes a second main core 631and a second auxiliary core 632, a field magnet 641, and a commutatormagnet 643.

First Rotor Core 620

The first rotor core 620 includes the first main core 621 and the firstauxiliary core 622 that are stacked in the direction of the axis L. Thefirst main core 621 and the first auxiliary core 622 are formed bypressing a magnetic steel plate of a soft magnetic material.

The first main core 621 includes a base portion 623 that is disk-shaped.A through hole 623 a, to which the rotation shaft 619 is fixed, extendsthrough the center of the base portion 623. The base portion 623includes a boss 623 b, which is substantially cylindrical. The boss 623b is projected around the through hole 623 a and formed through aburring process. The boss 623 b projects from the base portion 623outward in the axial direction (away from the field magnet).

A plurality of (four in the present embodiment) first claw portions 624,which are arranged at equal intervals in the circumferential direction,project outward in the radial direction from the outer circumferentialsurface of the base portion 623 and extend in the axial direction. Eachfirst claw portion 624 includes a radially extending portion 625, whichextends outward in the radial direction from the outer circumferentialsurface of the base portion 623, and an axially extending portion 626,which extends in the direction of the axis L from a distal end of theradially extending portion 625. The radially extending portion 625 issectoral and extends about the axis L as viewed in the direction of theaxis L. An outer circumferential surface (radially outer surface) of theaxially extending portion 626 is arcuate and extends about the axis L.The radially extending portion 625 is bent by 90° to form the axiallyextending portion 626.

The first auxiliary core 622, which is stacked on the axially outer sideof the first main core 621 (away from the field magnet), is flat as awhole and includes a disk-shaped base portion 627 and extending portions628, which extend outward in the radial direction from the base portion627.

The base portion 627 is stacked on the base portion 623 of the firstmain core 621 in the direction of the axis L. The base portions 623 and627 of the first main core 621 and the first auxiliary core 622 have thesame outer diameter. A through hole 627 a, to which the boss 623 b onthe base portion 623 of the first main core 621 is fitted, extendsthrough the center of the base portion 627 of the first auxiliary core622. The first main core 621 and the first auxiliary core 622 may befixed to each other by press-fitting or adhering the boss 623 b to thethrough hole 627 a.

The number of the extending portions 628, which are extended radiallyoutward from the base portion 627 and arranged at equal intervals in thecircumferential direction, is the same as the first claw portions 624(four in the present embodiment). Each extending portion 628 is sectoraland extends about the axis L as viewed in the direction of the axis L.

The extending portions 628 are stacked on the radially extendingportions 625 of the first claw portions 624 in the direction of the axisL. The extending portions 628 have the same opening angle with respectto the axis L (circumferential width) as the radially extending portions625. The extending portions 628 have an outer diameter (length from theaxis L to outer circumferential end) that is larger than an outerdiameter of the first claw portions 624 (length from the axis L to theouter circumferential surfaces of the axially extending portions 626).Thus, when the first main core 621 and the first auxiliary core 622 arestacked upon each other (see FIG. 50), the distal side of the extendingportion 628 partially projects outward in the radial direction beyondthe axially extending portion 626 of the first claw portion 624.

In the present embodiment, as illustrated in FIG. 50, when the firstmain core 621 and the first auxiliary core 622 are stacked, the firstclaw portion 624 and the extending portion 628 form a first claw pole P1of the first rotor core 620.

Second Rotor Core 630

Referring to FIG. 49, the second rotor core 630 has the sameconfiguration as the first rotor core 620. The second rotor core 630includes the second main core 631, which is identical in shape to thefirst main core 621, and the second auxiliary core 632, which isidentical in shape to the first auxiliary core 622. More specifically,the second main core 631 includes a base portion 633 and second clawportions 634 (radially extending portion 635 and axially extendingportion 636) respectively corresponding to the base portion 623 and thefirst claw portions 624 of the first main core 621 (radially extendingportion 625 and axially extending portion 626). The second auxiliarycore 632 includes a base portion 637 and extending portions 638respectively corresponding to the base portion 627 and the extendingportions 628 of the first auxiliary core 622. When the second main core631 and the second auxiliary core 632 are stacked upon each other, thesecond claw portion 634 and the extending portion 638 form a second clawpole P2 of the second rotor core 630 in the same manner as in the firstrotor core 620.

The first rotor core 620 and the second rotor core 630 are coupled sothat the first claw poles P1 and the second claw poles P2 arealternately arranged at equal intervals in the circumferential direction(see FIG. 48). In the coupled state, the first and second claw portions624 and 634 have distal ends (axially extending portions 626 and 636)directed toward opposite directions, and the second claw portions 634are located between the first claw portions 624 in the circumferentialdirection. The axially extending portions 626 and 636 of the first andsecond claw portions 624 and 634 are alternately arranged at equalintervals in the circumferential direction.

Field Magnet 641

As illustrated in FIGS. 49 and 50, when the first and second rotor cores620 and 630 are coupled to each other, the base portions 623 and 633 ofthe first and second main cores 621 and 631 are parallel to each other,and the field magnet 641 is located in between.

The field magnet 641 is a disk-shaped permanent magnet. A through hole641 a extends through a central portion of the field magnet 641. Acylindrical sleeve 642 is inserted into the through hole 641 a, and therotation shaft 619 is inserted through the sleeve 642. The sleeve 642 isformed by a nonmagnetic body of the same stainless steel as the rotationshaft 619 in the present embodiment. The field magnet 641 hassubstantially the same outer diameter as the base portions 623 and 633of the first and second main cores 621 and 631. The field magnet 641 hasone axial end surface (upper surface as viewed in FIGS. 49 and 50) thatcontacts the base portion 623 of the first main core 621 and the anotheraxial end surface (lower surface) that comes into contact with the baseportion 633 of the second main core 631. The field magnet 641 is heldbetween and fixed in the axial direction by the base portions 623 and633.

The field magnet 641 is magnetized in the axial direction so that theportion closer to the first rotor core 620 serves as the N pole and theportion closer to the second rotor core 630 serves as the S pole. Thus,the field magnet 641 acts so that the first claw pole P1 (first clawportion 624 and extending portion 628) of the first rotor core 620functions as the N pole and the second claw pole P2 (second claw portion634 and extending portions 638) of the second rotor core 630 functionsas the S pole. In FIG. 49, the arrows in solid lines indicate themagnetized direction (direction from S pole to N pole) of the fieldmagnet 641 and the commutator magnet 643, which will be described later.

The rotor 612 of the present embodiment is a Lundell rotor that uses thefield magnet 641. As shown in FIG. 48, the first claw poles P1, servingas the N poles, and the second claw poles P2, serving as the S poles,are alternately arranged in the circumferential direction. The number ofmagnetic poles is eight.

Commutator Magnet 643

As illustrated in FIGS. 49 and 50, the rotor 612 includes the annularcommutator magnet 643 at an outer circumferential side of the fieldmagnet 641. The field magnet 641 and the commutator magnet 643 areformed from different materials. More specifically, the field magnet 641is an anisotropic sintered magnet, for example, and is formed by aferrite magnet, a samarium-cobalt (SmCo) based magnet, a neodymiummagnet, or the like. The commutator magnet 643 is a bonded magnet(plastic magnet, rubber magnet, or the like), for example, and is formedby a ferrite magnet, a samarium-iron-nitrogen (SmFeN) based magnet, asamarium-cobalt (SmCo) based magnet, a neodymium magnet, or the like.

As illustrated in FIG. 49, the commutator magnet 643 includes backsurface magnet portions 644 and 645 and interpolar magnet portions 646.The commutator magnet 643 is a polar anisotropic magnet magnetized toreduce magnetic flux leakage from the back surface magnet portions 644and 645 and the interpolar magnet portions 646.

More specifically, the surface magnet portions 644 are located betweenthe inner circumferential surfaces of the axially extending portions 626of the first claw portions 624 and the outer circumferential surface ofthe field magnet 641 (see FIG. 50). In each back surface magnet portion644, radial direction components are mainly magnetized so that the part(radially outer side) in contact with the inner circumferential surfaceof the axially extending portion 626 serves as the N pole, which is thesame polarity as the axially extending portion 626 (first claw pole P1).

The back surface magnet portions 645 are located between the innercircumferential surfaces of the axially extending portions 636 of thesecond claw portions 634 and the outer circumferential surface of thefield magnet 641. In each back surface magnet portion 645, radialdirection components are mainly magnetized so that the part (radiallyouter side) in contact with the inner circumferential surface of theaxially extending portion 636 serves as the S pole, which is the samepolarity as the axially extending portion 636 (second claw pole P2).

The interpolar magnet portions 646 are located between the first clawpoles P1 and the second claw poles P2 in the circumferential direction.In each interpolar magnet portion 646, circumferential directioncomponents are mainly magnetized so that the part closer to the firstclaw pole P1 in the circumferential direction serves as the N pole andthe portion closer to the second claw pole P2 in the circumferentialdirection serves as the S pole.

The operation of the seventh embodiment will now be described.

When the three-phase driving current is supplied to the coil 614 of thestator 611, a rotating magnetic field is formed at the stator 611. Therotating magnetic field rotates the rotor 612, which is located at theinner side of the stator 611.

Referring to FIG. 50, in the first claw pole P1 of the rotor 612, theaxially extending portion 626 of the first claw portion 624 opposes theinner circumferential surface 618 a of the distal tooth end 618 of thestator 611 in the radial direction. The extending portion 628 of thefirst auxiliary core 622 includes a section (axially opposing portion628 a) projecting outward in the radial direction from the axiallyextending portion 626 and opposing the first axial end surface 618 b ofthe distal tooth end 618 in the axial direction.

In the same manner, referring to FIG. 48, in the second claw pole P2,the axially extending portion 636 of the second claw portion 634 opposesthe inner circumferential surface 618 a of the distal tooth end 618 inthe radial direction. The extending portion 638 includes a section(axially opposing portion 638 a) projecting outward in the radialdirection from the axially extending portion 636 and opposing the secondaxial end surface 618 c of the distal tooth end 618 in the axialdirection.

Thus, the magnetic flux of the field magnet 641 acts on the innercircumferential surface 618 a of the distal tooth end 618 from theaxially extending portions 626 and 636 of the first and second clawportions 624 and 634. Further, the magnetic flux of the field magnet 641acts on first and second axial end surfaces 618 b and 618 c of thedistal tooth end 618 from the axially opposing portions 628 a and 638 aof the first and second auxiliary cores 622 and 632 (see the arrows inbroken lines in FIG. 50). The magnetic flux of the field magnet 641interacts with the rotating magnetic field of the stator 611 andgenerates rotational torque at the rotor 612.

The advantages of the seventh embodiment will now be described.

(19) The first claw pole P1 of the first rotor core 620 includes theaxially extending portion 626 (first claw portion 624), which opposesthe distal tooth end 618 in the radial direction, and the axiallyopposing portion 628 a (extending portion 628 of first auxiliary core622), which opposes the distal tooth end 618 in the axial direction. Thesecond claw pole P2 of the second rotor core 630 includes the axiallyextending portion 636 (second claw portion 634), which opposes thedistal tooth end 618 in the radial direction, and the axially opposingportion 638 a (extending portion 638 of second auxiliary core 632),which opposes the distal tooth end 618 in the axial direction.

In this configuration, surfaces of the first and second claw poles P1and P2 opposing the distal tooth end 618 are obtained in both radial andaxial directions. This widens the surface opposing the distal tooth end618. Thus, magnetic saturation is less likely to occur in the first andsecond claw poles P1 and P2. As a result, the magnetic flux generated bythe field magnet 641 effectively acts on the stator 611 from the axiallyextending portions 626 and 636 (radially opposing portion) and theaxially opposing portions 628 a and 638 a. Further, the output can beimproved.

(20) The first rotor core 620 is formed by joining the first main core621 and the first auxiliary core 622, which are separate components. Inthe same manner, the second rotor core 630 is formed by joining thesecond main core 631 and the second auxiliary core 632, which areseparate components. Further, the first and second main cores 621 and631 respectively include the radially opposing portions (axiallyextending portions 626 and 636) of the first and second claw poles P1and P2, and the first and second auxiliary cores 622 and 632respectively include the axially opposing portions 628 a and 638 a ofthe first and second claw poles P1 and P2.

This configuration forms the first and second claw poles P1 and P2including the radially opposing portions (the axially extending portions626 and 636) and the axially opposing portions 628 a and 638 a, whilesimplifying the shapes of the first and second main cores 621 and 631and the first and second auxiliary cores 622 and 632. Thus, the firstand second rotor cores 620 and 630, that is, the first and second maincores 621 and 631 and the first and second auxiliary cores 622 and 632may be formed through a simple and inexpensive means (for example,pressing) in a further preferred manner.

The seventh embodiment may be modified as described below.

In the seventh embodiment, the first and second auxiliary cores 622 and632 are respectively stacked on the outer sides of the first and secondmain cores 621 and 631 (the base portions 623 and 633) in the axialdirection (facing away from the field magnet) but may instead bestacked, for example, on the inner sides of the first and second maincores 621 and 631 in the axial direction (facing toward the field magnet641), as illustrated in FIGS. 51, 52, and 53. In FIGS. 51 to 53, samereference numerals are given to those components that are the same asthe corresponding components of the seventh embodiment. Such componentswill not be described in detail.

As illustrated in FIGS. 51 to 53, the base portion 627 of the firstauxiliary core 622 is stacked on the inner side of the base portion 623of the first main core 621 in the axial direction (facing toward thefield magnet 641). The axially extending portions 626 of the first clawportions 624 in the first main core 621 are inserted into insertionholes 628 b in the extending portions 628 of the first auxiliary core622. The extending portions 628 are stacked on the inner side of theradially extending portion 625 of the radially extending portions 625 inthe axial direction (facing toward the commutator magnet 643). Theextending portions 628 have the same opening angle (circumferentialwidth) with respect to the axis L as the radially extending portions625, and the axially extending portions 626 have a smaller opening anglethan the radially extending portions 625 and the extending portions 628.In such a configuration, the axially opposing portion 628 a facing thefirst axial end surface 618 b of the distal tooth end 618 in the axialdirection is located at the radially outer side of the insertion hole628 b of the extending portion 628. The second rotor core 630 ismodified in the same manner as the first rotor core 620. Thisconfiguration has the same advantages as the seventh embodiment.

The first rotor core 620 of the seventh embodiment is formed by joiningthe first main core 621, which includes the radially opposing portion(axially extending portion 626) of the first claw pole P1, and the firstauxiliary core 622, which includes the axially opposing portion 628 a ofthe first claw pole P1. In the same manner, the second rotor core 630 isformed by joining the second main core 631, which includes the radiallyopposing portion (axially extending portion 636) of the second claw poleP2, and the second auxiliary core 632, which includes the axiallyopposing portion 638 a of the second claw pole P2.

However, there is no limitation to such a configuration. For example, asshown in FIGS. 54 and 55, a first rotor core 650 a and a second rotorcore 650 b may each be formed by a single member. The first and secondrotor cores 650 a and 650 b have the same shape. In FIGS. 54 and 55,same reference numerals are given to those components that are the sameas the corresponding components of the seventh embodiment. Suchcomponents will not be described in detail.

As illustrated in FIG. 55, the first and second rotor cores 650 a and650 b, which are formed by pressing a magnetic steel plate of a softmagnetic material, each includes a disk-shaped base portion 651. Aplurality of (four in this example) claw poles 652 are arranged at equalintervals in the circumferential direction on the outer circumferentialsurface of the base portion 651. The claw poles 652 project outward inthe radial direction and extend in the axial direction. A portion of theclaw pole 652 extending outward in the radial direction from the outercircumferential surface of the base portion 651 defines a radiallyextending portion 653, and a portion of the claw pole 652 extending inthe direction of the axis L from the radially extending portion 653defines an axially extending portion 654. The claw pole 652 includes aprojection 655 projecting further radially outward from the radiallyextending portion 653. The claw pole 652 is bent at a right angle toform the axially extending portion 654 and leave the remainingprojection 655 that projects outward in the radial direction.

In the example of FIG. 55, two projections 655 are formed between threeaxially extending portions 654. Instead two axially extending portion654 may be formed between three projections 655.

In this configuration, as illustrated in FIG. 54, in the claw pole 652of the first rotor core 650 a, the axially extending portion 654 opposesthe inner circumferential surface 618 a of the distal tooth end 618 ofthe stator 611 in the radial direction. Each projection 655 of the clawpole 652 opposes the first axial end surface 618 b of the distal toothend 618 in the axial direction.

In the same manner, in the claw pole 652 of the second rotor core 650 b,the axially extending portion 654 opposes the inner circumferentialsurface 618 a of the distal tooth end 618 in the radial direction. Eachprojection 655 opposes the second axial end surface 618 c of the distaltooth end 618 in the axial direction.

In the same manner as the seventh embodiment, the claw pole 652 of thisconfiguration obtains a surface opposing the distal tooth end 618 inboth of the radial direction and the axial direction. Further, thesurface opposing the distal tooth end 618 is widened. This limitsmagnetic saturation in the claw poles 652. Thus, the magnetic fluxgenerated by the field magnet 641 effectively acts on the stator 611,and the output is improved. Moreover, in this configuration, the firstand second rotor cores 650 a and 650 b are each formed by a singlemember. This keeps the number of components low, which is desirable interms of managing components.

In the configuration illustrated in FIG. 54, the magnetic flux generatedby the back surface magnet portion 644 and 645 (commutator magnet 643)located on the back side (inner circumferential side) of the axiallyextending portion 654 at a location where the rotor 612 and the distaltooth end 618 oppose each other in the radial direction, partially actsdirectly on the stator 611 through a gap formed between the axiallyextending portions 654.

In the configuration illustrated in FIG. 55, the first and second rotorcores 650 a and 650 b are formed through pressing but instead may beformed through, for example casting. This allows gaps to be eliminatedfrom between the axially extending portions 654 and the projections 655,while forming each of the first and second rotor cores 650 a and 650 bfrom a single member.

In the seventh embodiment, the field magnet 641 and the commutatormagnet 643 are formed from different materials but instead may be formedfrom the same material. Further, the commutator magnet 643 may beomitted from the seventh embodiment.

The number of the first and second claw poles P1 and P2 (number ofmagnetic poles) is not limited to that in the seventh embodiment and maybe changed in accordance with the configuration.

In the seventh embodiment, the present invention is applied to an innerrotor type motor in which the rotor 612 is located at the inner side ofthe stator 611. Alternatively, the present invention may be applied toan outer rotor type motor.

The seventh embodiment and its modifications may be combined asrequired.

The invention claimed is:
 1. A motor comprising a rotor, wherein therotor includes: first and second rotor cores, wherein the first andsecond rotor cores each include a disk-shaped core base and a pluralityof claw poles arranged in a circumferential direction on an outercircumferential portion of the core base, and the first and second rotorcores are stacked upon each other in an axial direction so that the clawpoles of the first rotor core and the claw poles of the second rotorcore are alternately arranged in the circumferential direction; a fieldmagnet that is located between the core base of the first rotor core andthe core base of the second rotor core, the field magnet is magnetizedin the axial direction so that the claw poles of the first rotor coreand the claw poles of the second rotor core function as differentmagnetic poles in the circumferential direction; and a commutator magnetthat is located on an outer circumference of the field magnet and nearthe claw poles, wherein the commutator magnet is magnetized so thatsurfaces having the same polarity face each other in the claw poles andthe commutator magnet, wherein the field magnet and the commutatormagnet are formed integrally as an integrated permanent magnet, thecommutator magnet includes a plurality of back surface magnet portionsand a plurality of interpolar magnet portions, the back surface magnetportions are located between the claw poles and the field magnet, andthe back surface magnet portions are magnetized to limit magnetic fluxleakage from where the back surface magnet portions are located, theinterpolar magnet portions are located between adjacent ones of the backsurface magnet portion in the circumferential direction, and theinterpolar magnet portions are magnetized to limit magnetic flux leakagefrom where the interpolar magnet portions are located, the back surfacemagnet portions and the interpolar magnet portions are located within anaxial range that is the same as an axial range in which the field magnetis formed, and the integrated permanent magnet includes two axial endsurfaces and a groove formed on at least one of the two axial endsurfaces, the groove being arranged at a boundary of the field magnetwith the back surface magnet portions and the interpolar magnetportions.
 2. The motor according to claim 1, wherein the integratedpermanent magnet includes a circular outer circumference that extendsalong radially inner end surfaces of the claw poles.
 3. The motoraccording to claim 1, wherein the groove has a circular shape as viewedin the axial direction.